String.replaceAll() Not a Function Error: Causes and Solutions

The TypeError: string.replaceAll is not a function error occurs when attempting to use the replaceAll() method in environments where it's not yet supported. This comprehensive guide explains the root causes and provides practical solutions.

Problem Overview

The replaceAll() method was introduced in ECMAScript 2021 (ES12) and provides a convenient way to replace all occurrences of a substring within a string:

let string = ":insertx: :insertx: :inserty: :inserty: :insertz: :insertz:";
let newstring = string.replaceAll(":insertx:", 'hello!');

WARNING

If you encounter "replaceAll is not a function", your JavaScript environment doesn't support this modern method yet.

Browser and Runtime Compatibility

replaceAll() has varying support across environments:

• Chrome: Available since version 85 (released August 2020)
• Firefox: Available since version 77 (released June 2020)
• Safari: Available since version 13.1 (released March 2020)
• Node.js: Available since version 15.0.0 (released October 2020)

INFO

Always check the MDN compatibility table for current browser support.

Recommended Solutions

1. Use replace() with Regular Expression (Most Compatible)

The most widely supported approach uses replace() with a global regex pattern:

let string = ":insertx: :insertx: :inserty: :inserty: :insertz: :insertz:";
let newstring = string.replace(/:insertx:/g, 'hello!');
console.log(newstring);
// Output: "hello! hello! :inserty: :inserty: :insertz: :insertz:"

2. Generic replaceAll Implementation with Escaping

For dynamic replacements where the search string might contain regex special characters, use this helper function:

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
}

function replaceAll(str, match, replacement) {
  return str.replace(new RegExp(escapeRegExp(match), 'g'), replacement);
}

// Examples
console.log(replaceAll('a.b.c.d.e', '.', '__')); // "a__b__c__d__e"
console.log(replaceAll('cost: $10.50', '$', 'USD ')); // "cost: USD 10.50"

DANGER

Always escape special regex characters when using dynamic patterns to prevent unexpected behavior.

3. Split and Join Approach

For simple string replacements without regex capabilities:

let string = ":insertx: :insertx: :inserty: :inserty: :insertz: :insertz:";
let newstring = string.split(":insertx:").join('hello!');

Advanced Solutions

Polyfill Implementation

For environments where you need replaceAll() support but can't update, add this polyfill:

if (typeof String.prototype.replaceAll === "undefined") {
  String.prototype.replaceAll = function(match, replacement) {
    // Escape regex special characters for safe replacement
    const escapedMatch = match.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
    return this.replace(new RegExp(escapedMatch, 'g'), replacement);
  };
}

TIP

Consider using established polyfill libraries like core-js instead of custom implementations for production code.

Using Core-JS Polyfill

For a more robust solution with npm:

1. Install core-js types:

npm install @types/core-js --save

2. Create a declaration file (polyfill.d.ts):

declare module 'core-js/features/string/replace-all';

3. Conditionally load the polyfill:

if (!String.prototype.replaceAll) {
  import('core-js/features/string/replace-all');
}

When to Use Each Approach

Approach	Best For	Considerations
replace() with regex	Maximum compatibility	Requires regex knowledge
Split and join	Simple replacements	Less performant for large strings
Custom polyfill	Projects needing modern syntax	Maintenance responsibility
Core-js polyfill	Production applications	Adds to bundle size

Performance Considerations

For most use cases, the performance differences between these approaches are negligible. However:

• Regex replacement is generally fastest for complex patterns
• Split/join can be slower with very large strings
• Polyfills add minimal overhead but increase bundle size

Conclusion

The replaceAll() method provides convenient syntax but requires modern JavaScript environments. For broad compatibility, use replace() with global regex patterns. For projects targeting modern browsers and Node.js versions (Chrome 85+, Firefox 77+, Safari 13.1+, Node.js 15+), you can safely use replaceAll() directly.

Always test your target environments and consider polyfills or alternative approaches when supporting older browsers is required.