How to Fix JavaScript Error in Breeze.debug.js

As a developer, I’ve had my fair share of headaches when trying to run web applications on different environments. One particularly frustrating issue I encountered recently involved the SCRIPT1028 JavaScript error while working with the Breeze library on Windows 8. This error occurred when I ran my Single Page Application (SPA) in an internal Internet Explorer (IE) browser.

The error message pointed to line 4663 in breeze.debug.js, causing the application to fail in a way that wasn’t happening on other machines (like my Windows 7 setup). If you’re encountering this issue, you’re not alone. Let me walk you through the problem, how I fixed it, and some additional tips to avoid similar errors in the future.

Error Explanation

When I was running the application on Windows 8, I received the following JavaScript error:

: Expected identifier, string or number at line 4663, column 13 in http://localhost:50033/Script/breeze.debug.js

This error typically happens due to syntax issues in JavaScript, often arising from things like misplaced commas, missing identifiers, or incompatible JavaScript features across browsers. The cause of this issue, in my case, was a trailing comma in an object literal, which some versions of Internet Explorer (IE) do not handle well, especially in older environments like Windows 8.

Code Example:

Here’s a snippet from the problematic code:

entityType = new EntityType({
    shortName: shortName,
    namespace: namespace,  // <==== Line 4663 (Trailing comma issue)
});

The trailing comma after the namespace property was causing IE on Windows 8 to throw an error. In contrast, modern browsers like Chrome or Edge don’t mind this comma. However, IE (especially versions running on older Windows environments) fails to interpret it correctly, leading to the SCRIPT1028 error.

Fix the Syntax Error

The fix is simple: Remove the trailing comma after namespace: namespace:

entityType = new EntityType({
    shortName: shortName,
    namespace: namespace // Remove the comma after 'namespace' here
});

Once I made this change, the error was resolved, and the application worked fine in IE on Windows 8.

However, fixing this specific error brought me to another challenge another JavaScript runtime error.

Error 0x800a01b6 – JavaScript Runtime Error

After fixing the trailing comma, I encountered another error:

Unhandled exception at line 1271, column 17 in http://localhost:50033/Scripts/breeze.debug.js
0x800a01b6 - JavaScript runtime error: Object doesn't support property or method 'some'

This error is related to the following code snippet in the Breeze library:

self._compiledFn = function (that, v) {
    return that._fns.some(function (fn) {
        return fn(that, v);
    });
};

The error message "Object doesn't support property or method 'some'" suggests that self._fns is either null or undefined at runtime, which causes JavaScript to fail when trying to call .some() on it.

Ensuring _fns is Always an Array

To fix this error, we need to make sure that self._fns is always an array before calling .some() on it. You can easily add a check to initialize _fns as an empty array if it’s not already defined:

self._fns = self._fns || [];  // Ensure _fns is an array before using .some()

self._compiledFn = function (that, v) {
    return that._fns.some(function (fn) {
        return fn(that, v);
    });
};

With this fix, if self._fns is undefined or null, it will be initialized as an empty array. This ensures that .some() works as expected and prevents the runtime error.

Best Practices for Avoiding Similar Error

Now that we’ve fixed these errors, let me share some additional practices that can help prevent similar issues and improve the robustness of your code:

• Check for Undefined or Null Values:
  Before performing operations on variables (especially arrays or objects), always check that they are not null or undefined. This can save you from runtime errors.

if (!self._fns || !Array.isArray(self._fns)) {
    self._fns = [];  // Initialize as empty array if not already an array
}

• Use Modern JavaScript:
  Consider using modern JavaScript features like const, let, and arrow functions for cleaner, more readable code. Here’s an example of how you can convert your function to use an ES6 arrow function.

._compiledFn = (that, v) => {
    return that._fns.some(fn => fn(that, v));
};

Arrow functions are not only shorter but also lexically bind this, making your code easier to understand and debug.

• Ensure Browser Compatibility:
  Since you’re encountering issues with Internet Explorer, it’s essential to test your code across multiple browsers, especially for older versions like IE. Use polyfills or transpiling tools like Babel to ensure compatibility with older browsers.
• Log and Debug:
  Use console.log() to inspect the values of variables like _fns to ensure they contain the expected data at runtime. Logging helps you track down issues before they cause errors in production.

console.log(self._fns);
if (Array.isArray(self._fns)) {
    console.log('Valid array:', self._fns);
}

Conclusion

Fixing SCRIPT1028 and 0x800a01b6 errors in your Breeze application may seem daunting at first, but the solutions are straightforward once you understand the root causes. By removing trailing commas in your JavaScript objects and ensuring that your arrays are properly initialized, you can avoid these issues. Additionally, by adhering to best practices like checking for null values, using modern JavaScript, and testing across different browsers, you can make your code more resilient and cross-browser compatible.