How to Check if an Array Contains Another Array in JavaScript?

Can You Check if an Array Contains Another in JavaScript?

Similar to PHP's in_array() function, which compares values from one array against another, JavaScript does not have a built-in equivalent for this functionality.

Workarounds

To address this gap, popular JavaScript libraries and utility packages provide their own implementations. jQuery's $.inArray() and Prototype's Array.indexOf() are notable examples. jQuery's implementation is straightforward:

function inArray(needle, haystack) {
  for (var i = 0; i < haystack.length; i++) {
    if (haystack[i] == needle) return true;
  }
  return false;
}

Array Comparison

However, it's important to note that PHP's in_array() also determines if one array is within another. Chris's and Alex's code does not replicate this behavior. Instead, Chris's code is similar to PHP's array_intersect, while Alex's is Prototype's official version of indexOf.

To implement PHP's in_array() for nested arrays, the following custom function can be used:

function arrayCompare(a1, a2) {
  if (a1.length != a2.length) return false;
  for (var i = 0; i < a1.length; i++) {
    if (a1[i] !== a2[i]) return false;
  }
  return true;
}

Enhanced inArray() Function:

function inArray(needle, haystack) {
  for (var i = 0; i < haystack.length; i++) {
    if (typeof haystack[i] == 'object') {
      if (arrayCompare(haystack[i], needle)) return true;
    } else {
      if (haystack[i] == needle) return true;
    }
  }
  return false;
}

Example Usage

var a = [['p', 'h'], ['p', 'r'], 'o'];

if (inArray(['p', 'h'], a)) {
  alert('ph was found');
}
if (inArray(['f', 'i'], a)) {
  alert('fi was found');
}
if (inArray('o', a)) {
  alert('o was found');
}

Output:

ph was found
o was found

Please note that extending the Array prototype is not recommended, as it can have unintended consequences.

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