JavaScript policy runtime error troubleshooting

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ScriptExecutionFailed

Error code

steps.javascript.ScriptExecutionFailed

Error response body

{
    "fault": {
        "faultstring": "Execution of javascript_policy_name failed with error: error_type: error_description. (javascript_source_file_name)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Types of Errors and possible causes

The JavaScript policy can throw many different types of ScriptExecutionFailed errors. Some of the more commonly seen errors are listed in the table below:

Type of Error	Cause
Range Error	A RangeError is thrown if you use a number that is outside the range of legal values.
Reference Error	A ReferenceError is thrown if you use (reference) a variable that has not been declared.
Syntax Error	A SyntaxError is thrown if you try to evaluate code with a syntax error.
Type Error	A TypeError is thrown if you use an operation that is outside the range of expected types.
URI Error	A URIError is thrown if you use illegal characters in a URI function.

Range error

The error type RangeError is thrown when you operate on a value or pass a value to a function that is not in the set or range of allowed values.

For example, this error is thrown under the following circumstances:

If you use an invalid date such as Sep 31st 2018 with some of the Date APIs.
If you pass an invalid value to numeric methods such as Number.toPrecision(), Number.tofixed(), or Number.toExponential(). For example, let's say you pass a large value like 400 or 500 in the Number.toPrecision() method you will see a range error.
If you create an array with illegal length.

Error response body

{
    "fault": {
        "faultstring": "Execution of javascript_policy_name failed with error: Javascript runtime error: \"RangeError: error_description. (javascript_source_file_name:line_number)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Note: The diagnosis and resolution of range errors depends on the exact error message thrown by the JavaScript policy. A couple of examples are described below for your reference.

Example 1: Invalid Date

Example error response body

{
    "fault": {
        "faultstring": "Execution of ParseDate failed with error: Javascript runtime error: \"RangeError: Date is invalid. (ParseDate.js:2)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Diagnosis

Identify the JavaScript policy, its source file, the line number where the error occurred and the error description. You can find all this information in the faultstring element of the error response. For example, in the following faultstring, the JavaScript policy name is ParseDate, the JavaScript source file is ParseDate.js, the line number at which the error occurred is 2 and the error description is Date is invalid:
```
"faultstring": "Execution of ParseDate failed with error: Javascript runtime error: \"RangeError: Date is invalid. (ParseDate.js:2)\""
```
Examine the JavaScript source file (identified in step #1 above) and check if there is an invalid date being used in the line number specified in the error or if the variable used in the line number has an invalid date. If an invalid date is used, then that's the cause of the error.

Here's a sample JavaScript source file that leads to this error:

ParseDate.js
```
var date = new Date('2018-09-31T11:19:08.402Z');
date.toISOString();
```
In this example, there's a variable date used in the line number 2. Examining the source file, you can see that the date variable is set with an invalid date: 2018-09-31T11:19:08.402Z. This date is invalid because September does not have 31 days.

Note: The ISO-8601 format used in this example is: YYYY-MM-DDTHH:mm:ss.sssZ

Resolution

Ensure that you always use a valid date while using Date APIs in the JavaScript code.

To fix the example JavaScript code shown above, you can set the date as Sept 30 2018 as shown below:

var date = new Date('2018-09-30T11:19:08.402Z');
date.toISOString();

Example 2: Invalid number passed to Precision APIs

Example error response body

{
    "fault": {
        "faultstring": "Execution of SetNumberPrecision failed with error: Javascript runtime error: "RangeError: Precision 400 out of range. (SetNumberPrecision.js:2)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Diagnosis

Identify the JavaScript policy, its source file, the line number where the error occurred, and the error description. You can find all this information in the faultstring element of the error response. For example, in the following faultstring, the JavaScript policy name is SetNumberPrecision, the JavaScript source file is SetNumberPrecision.js, the line number at which the error occurred is 2 and the error description is Precision 400 out of range.
```
"faultstring": "Execution of SetNumberPrecision failed with error: Javascript runtime error: "RangeError: Precision 400 out of range. (SetNumberPrecision.js:2)\""
```
Examine the JavaScript source file (identified in step #1 above). If the large number mentioned as part of the error description is used in the specific line number, then that's the cause for the error.

Here's a sample JavaScript source file that leads to this error:

SetNumberPrecision.js
```
var number = 12.3456;
var rounded_number = number.toPrecision(400);
print("rounded_number = " + rounded_number);
```
In this example, notice that a large value of 400 is used in line number 2. Because you can't set the precision to such a large number of digits, you get the below error:
```
"faultstring": "Execution of SetNumberPrecision failed with error: Javascript runtime error: "RangeError: Precision 400 out of range. (SetNumberPrecision.js:2)\""
```

Resolution

Ensure that the number used in the toPrecision() method is within the set of allowed values.

To fix the issue with the example JavaScript described above, set the number of significant digits to 2 which is valid:

var number = 12.3456;
var rounded_number = number.toPrecision(2);
print("rounded_number = " + rounded_number);

Reference error

The error type ReferenceError is thrown when an undefined variable in your JavaScript is used (referenced) or operated on.

Error response body

{
    "fault": {
        "faultstring": "Execution of javascript_policy_name failed with error: Javascript runtime error: \"ReferenceError: variable_name is not defined. (javascript_source_file_name:line_number)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Example error response body

{
    "fault": {
        "faultstring": "Execution of ComputeTotalPrice failed with error: Javascript runtime error: \"ReferenceError: \"price\" is not defined. (ComputeTotalPrice.js:3)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Diagnosis

Identify the JavaScript policy, its source file, and the line number where the undefined variable is referenced. You can find all this information in the faultstring element of the error response. For example, in the following faultstring, the JavaScript policy name is ComputeTotalPrice, the corresponding source file is ComputeTotalPrice.js, line number at which the error occurred is 3 and the undefined variable name is price.
```
"faultstring": "Execution of ComputeTotalPrice failed with error: Javascript runtime error: \"ReferenceError: \"price\" is not defined. (ComputeTotalPrice.js:3)\""
```
Examine the line number in the JavaScript source file and verify if the undefined variable identified in step #1 above, is being referenced. For example, the following JavaScript code references the undefined variable price in line 3, which matches with what's in the faultstring:

ComputeTotalPrice.js
```
var item = context.getVariable("request.queryparam.item");
var quantity = context.getVariable("request.queryparam.quantity");
var totalprice = parseInt(quantity) * parseInt(price);
context.setVariable("TotalPrice", totalprice);
```
Check if the specific variable is defined within the JavaScript code. If the variable is not defined, then that's the cause of the error.

In the example script shown above, the undeclared/defined price variable is used; therefore, you will see the below error:
```
"faultstring": "Execution of ComputeTotalPrice failed with error: Javascript runtime error: \"ReferenceError: \"price\" is not defined. (ComputeTotalPrice.js:3)\""
```

Resolution

Ensure that all the variables referenced in the JavaScript code are properly defined.

To fix the issue with the example JavaScript shown above, define the variable price before using it. For example:

var item = context.getVariable("request.queryparam.item");
var quantity = context.getVariable("request.queryparam.quantity");
var price = context.getVariable("request.queryparam.price");
var totalprice = parseInt(quantity) * parseInt(price);
context.setVariable("TotalPrice", totalprice);

Syntax error

The error type SyntaxError is thrown when the JavaScript engine encounters tokens or a token order that does not conform to the syntax of the language, or when an invalid format input is passed to the parser APIs such as JSON/XML parse.

For example, if the invalid or malformed JSON payload is passed as the input to the JSON.parse API used within the JavaScript policy, then you get this error.

Error response body

{
    "fault": {
        "faultstring": "Execution of javascript_policy_name failed with error: Javascript runtime error: \"SyntaxError: error_description. (javascript_source_file_name:line_number)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Example error response body

{
    "fault": {
        "faultstring": "Execution of ParseJSONRequest failed with error: Javascript runtime error: \"SyntaxError: Unexpected token: <. (ParseJSONRequest.js:2)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Diagnosis

Identify the JavaScript policy, its source file, the line number where the error occurred, and the error description. You can find all this information in the faultstring element of the error response. For example, in the following faultstring, the JavaScript policy name is ParseJSONRequest, the JavaScript source file is ParseJSONRequest.js, the line number at which the error occurred is 2 and the error description is Unexpected token:
```
"faultstring": "Execution of ParseJSONRequest failed with error: Javascript runtime error: \"SyntaxError: Unexpected token: <. (ParseJSONRequest.js:2)\""
```
Examine the line number 2 in the JavaScript source file (identified in step #1 above) and check what operation is being performed. If a JSON.parse() function is being executed then check the input parameter passed to it. If the input parameter is not valid or is malformed JSON, then that's the cause for the error.

Here's a sample JavaScript code that leads to this error:
```
var input = context.getVariable("request.content");
var result = JSON.parse(input);
```
In this example, the request payload (request.content) passed to the API Proxy is used as the input to JSON.parse() function.

Here's the sample API call that shows how the request was passed:
```
curl -v "http://<org>-<env>.apigee.net/v1/js-demo" -H "Content-Type: application/json" -X POST -d '<city>Bangalore</city>'
```
In the above request, the following XML payload is passed to the API Proxy <city>Bangalore</city>. The JSON.parse API expects a valid JSON to be passed but because an XML payload is passed instead, it fails with the below error:
```
"Execution of ParseJSONRequest failed with error: Javascript runtime error: \"SyntaxError: Unexpected token: <. (ParseJSONRequest.js:2)\""
```

Resolution

Be sure to pass valid input to the parse APIs used in the JavaScript code.

To fix the issue with the sample policy discussed above, pass a valid JSON payload request as follows:

curl -v "http://<org>-<env>.apigee.net/v1/js-demo" -H "Content-Type: application/json" -X POST -d '{"city" : "Bangalore"}'

Type error

The error type TypeError is thrown when:

An operand or argument passed to a function is incompatible with the type expected by that operator or function.
A function is invoked on a null, undefined or wrong object.
A property is accessed from a null, undefined or wrong object.

For example, a type error is thrown:

If you attempt to invoke the toUpperCase() function on a number. This is because the toUpperCase() function can be invoked only on string objects.
If you attempt to read a property from a null or undefined object.

Error response body

{
    "fault": {
        "faultstring": "Execution of javascript_policy_name failed with error: Javascript runtime error: \"TypeError: error_description. (javascript_source_file_name:line_number)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Example 1: Invoking a function on the wrong object

If you attempt to invoke a function on an unsupported object, then you get this error. For example, if you attempt to invoke the toUpperCase() function on a number you get the error. This is because the toUpperCase() function can be invoked only on string objects.

Example error response body

{
    "fault": {
        "faultstring": "Execution of ConvertToUpperCase failed with error: Javascript runtime error: \"TypeError: Cannot find function toUpperCase in object 100. (ConvertToUpperCase.js:2)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Diagnosis

Identify the JavaScript policy, its source file, the line number where the error occurred, and the error description. You can find all this information in the faultstring element of the error response. For example, in the following faultstring, the JavaScript policy name is ConvertToUpperCase, the source file is ConvertToUpperCase.js, the line number is 2 and the error description is **Cannot find function toUpperCase in object 100.
```
"faultstring": "Execution of ConvertToUpperCase failed with error: Javascript runtime error: \"TypeError: Cannot find function toUpperCase in object 100. (ConvertToUpperCase.js:2)\""
```
The error description indicates that you are invoking the function toUpperCase() on an object whose numeric value is 100.
Examine the JavaScript source file and verify if you are invoking the function toUpperCase() on an object whose numeric value is 100 at line number 2 (identified in step # 1 above). If yes, then that's the cause of the error.

Here's a sample JavaScript source file that leads to this error:

ConvertToUpperCase.js
```
var number = 100;
var result = number.toUpperCase();
```
In the JavaScript code shown above, the variable number is set with a value of 100. Subsequently the toUpperCase()( function is invoked on the number object. Since toUpperCase() function can be invoked only on string objects, you get the error:
```
"Execution of ConvertToUpperCase failed with error: Javascript runtime error: \"TypeError: Cannot find function toUpperCase in object 100. (ConvertToUpperCase.js:2)\""
```

Resolution

Always use functions such as toUpperCase() on valid objects.

To correct the example shown above, you can create a string variable and then invoke the toUpperCase() function on a string:

var text = "Hello Apigee !";
var result = text.toUpperCase();

Example 2: Cannot read property from an undefined object

If you attempt to access/read a property from an undefined object, then you get this error. For example, this error can occur when you attempt to access data from an object in an array, but the object is undefined. See the detailed explanation below.

Example error response body

{
    "fault": {
        "faultstring": "Execution of ParseJSONResponse failed with error: Javascript runtime error: \"TypeError: Cannot read property \"length\" from undefined. (ParseJSONResponse.js:7)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Diagnosis

Identify the JavaScript policy, its source file, the line number where the error occurred and the error description. You can find all this information in the faultstring element of the error response. For example, in the following faultstring, policy name is ParseJSONResponse, the source file is ParseJSONResponse.js, the line number is 6 and the error description is Cannot read property "length" from undefined.
```
"faultstring": "Execution of ParseJSONResponse failed with error: Javascript runtime error: \"TypeError: Cannot read property \"length\" from undefined. (ParseJSONResponse.js:6)\""
```
The error indicates that the property length cannot be read from an undefined object.
Examine the line number in the JavaScript source file (identified in step #1 above) and verify if the object has a valid value or is undefined. You may have to read and understand the complete source file to determine how the specific object was defined or derived and determine why the object is found to be undefined. If you find that the specific object is indeed undefined and you are trying to access the property length from it, then that's the cause of the error.

Let's look at an example to understand this issue better:
1. Assume that you receive the following JSON response from the backend server:
```
{
    "cars": [
       { "name":"Toyota", "count": 150 }
       { "name":"Honda", "count": 100 },
       { "name":"Ford", "count": 75 }
    ]
}
```
2. Here's a sample JavaScript source file that parses this JSON response and leads to the error mentioned above:
  
  ParseJSONResponse.js
```
// Get the JSON response
var jsonData = context.getVariable("response.content");
print (jsonData);

// Read the cars array
for (var i = 0; i < jsonData.cars.length; i++)
  {
  print("name = " + jsonData.cars[i].name);
  print("count = " + jsonData.cars[i].count);
  }
```
3. Examining the JavaScript code carefully you can see that in line number 2, the response.contentis read/stored to the variable jsonData as a regular string (in quotes).
4. Because jsonData is a regular string, when you attempt to access cars from jsonData (jsonData.cars) will be undefined.
5. Subsequently, when you attempt to read the property length from jsonData.cars, which is undefined, you get the error:
```
"faultstring": "Execution of ParseJSONResponse failed with error: Javascript runtime error: \"TypeError: Cannot read property \"length\" from undefined. (ParseJSONResponse.js:6)\""
```

Resolution

Ensure that you always read JSON data as a JSON object using the relevant JSON APIs.

To fix the example JavaScript described above, you can use the JSON.parse() function on the response.content object to get it as a JSON object. After this, you can access the cars array and iterate through the array successfully.

// Get the JSON response
var data = context.getVariable("response.content");
var jsonData = JSON.parse(data);
print (jsonData);

// Read the cars array
for (var i = 0; i < jsonData.cars.length; i++)
{
    print("name = " + jsonData.cars[i].name);
    print("count = " + jsonData.cars[i].count);
}

URI Error

The error type URIError is thrown if you use illegal characters in a URI function. For example, if you pass a URI which has a percentage symbol to the decodeURI or decodeURIComponent functions, then you will get this error.

Error response body

{
    "fault": {
        "faultstring": "Execution of javascript_policy_name failed with error: Javascript runtime error: \"URIError: error_description. (javascript_source_file_name:line_number)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Example error response body

{
    "fault": {
        "faultstring": "Execution of URIDecode failed with error: Javascript runtime error: \"URIError: Malformed URI sequence. (URIDecode.js:2)\"",
        "detail": {
            "errorcode": "steps.javascript.ScriptExecutionFailed"
        }
    }
}

Diagnosis

Identify the JavaScript policy, its source file, the line number where the error occurred, and the error description. You can find all this information in the faultstring element of the error response. For example, in the following faultstring, the JavaScript policy name is URIDecode</code the JavaScript source file is URIDecode.js, the line number is 2 and the error description is Malformed URI sequence:
```
"faultstring": "Execution of URIDecode failed with error: Javascript runtime error: \"URIError: Malformed URI sequence. (URIDecode.js:2)\""
```
The error description indicates that a malformed URI sequence is used in line number 2 of URIDecode.js.
Examine the JavaScript source file and verify if the argument passed to any of the URI functions contains any illegal characters. If yes, then that's the cause of error.

Here's an example JavaScript source file that leads to this error:

URIDecode.js
```
var str = "75%-Completed";
var decoded_str = decodeURIComponent(str);
context.setVariable("decoded_str", decoded_str);
```
In the example JavaScript code shown above, the variable str passed to decodeURIComponent() has a percentage symbol, which is considered an illegal character; therefore, you get the error:
```
"Execution of URIDecode failed with error: Javascript runtime error: \"URIError: Malformed URI sequence. (URIDecode.js:2)\""
```

Resolution

Ensure that all the characters used in URI functions are legal and permitted.

To fix the issue with the example JavaScript described above, use encode the percentage symbol. For example, %25:

var str = "75%25-Completed";
var decoded_str = decodeURIComponent(str);
context.setVariable("decoded_str", decoded_str);