How Can I Efficiently Check if an Item Exists in a JavaScript Array?

Best Way to Find if an Item Is in a JavaScript Array

Finding an object within an array is a common task in JavaScript programming. The ideal approach depends on browser compatibility and performance considerations.

Modern Solution: Includes()

For modern browsers compatible with ECMAScript 2016, use the includes() method. It simplifies the search:

arr.includes(obj);

Fallback for Older Browsers: IndexOf

For browsers without includes(), use indexOf with a comparison to -1:

function include(arr, obj) {
  return (arr.indexOf(obj) != -1);
}

Custom Implementations for Compatibility

For browsers like IE6-8 that don't support indexOf, define your own implementation:

// Mozilla's version
if (!Array.prototype.indexOf) {
  Array.prototype.indexOf = function(searchElement /*, fromIndex */) {
    // Implementation omitted for brevity
  };
}

// Daniel James's version
if (!Array.prototype.indexOf) {
  Array.prototype.indexOf = function (obj, fromIndex) {
    // Implementation omitted for brevity
  };
}

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