jQuery jQuery.grep() Method

What You’ll Learn

The jQuery.grep() utility finds array elements that pass a test function and returns them in a new array. This tutorial covers syntax, the optional invert flag, five worked examples, comparisons with Array.filter() and $.map(), and pitfalls every beginner should know.

Introduction

Filtering is one of the most common data tasks: keep the items that match a rule and discard the rest. jQuery provides jQuery.grep() (also written $.grep()) as a static utility that walks an array-like collection, runs your test function on each element, and builds a new array of matches.

The name comes from the Unix grep command, which searches text for patterns. In jQuery, the idea is the same spirit — find what fits — but your “pattern” is any JavaScript function that returns true or false.

Understanding the jQuery.grep() Method

jQuery.grep(array, callback [, invert]) calls your callback for each element with (element, index). When invert is omitted or false, elements where the callback returns true are copied into the result. When invert is true, elements where the callback returns false are kept instead.

Choose $.grep() when you need a filtered subset of an array without transforming values — prices above a threshold, items after a certain index, or everything except a banned value.

📝 Syntax

General form of jQuery.grep:

jQuery.grep( array, callback(element, index) [, invert ] )
// or
$.grep( array, callback(element, index) [, invert ] )

Parameters

• array — an array or array-like object (with length and indexed values) to search through.
• callback — a function that receives (element, index) and must return a boolean. Inside the callback, this refers to the global object (window in browsers).
• invert (optional) — when true, keep elements where the callback returns false; when false or omitted, keep elements where the callback returns true.

Return value

• A new array containing the filtered elements.
• The original array argument is not modified.

Minimal workflow

var positives = $.grep([0, 1, 2], function (n) {
  return n > 0;
});

console.log(positives); // [1, 2]

Examples Gallery

Each example uses $.grep(). Open DevTools or use the Try-it links to run them interactively.

var result = $.grep([0, 1, 2], function (n) {
  return n > 0;
});

console.log(result); // [1, 2]

[1, 2]

var inverted = $.grep([0, 1, 2], function (n) {
  return n > 0;
}, true);

console.log(inverted); // [0]

[0]

var arr = [1, 9, 3, 8, 6, 1, 5, 9, 4, 7, 3, 8, 6, 9, 1];

var filtered = $.grep(arr, function (n, i) {
  return n !== 5 && i > 4;
});

console.log(filtered.join(", "));
// "6, 1, 9, 4, 7, 3, 8, 6, 9, 1"

6, 1, 9, 4, 7, 3, 8, 6, 9, 1

var arr = [1, 9, 3, 8, 6, 1, 5, 9, 4, 7, 3, 8, 6, 9, 1];

arr = $.grep(arr, function (n, i) {
  return n !== 5 && i > 4;
});

arr = $.grep(arr, function (n) {
  return n !== 9;
});

console.log(arr.join(", "));
// "6, 1, 4, 7, 3, 8, 6, 1"

6, 1, 4, 7, 3, 8, 6, 1

var words = ["go", "run", "fly", "jump", "sit", "code"];

var longWords = $.grep(words, function (word) {
  return word.length > 3;
});

console.log(longWords.join(", "));
// "jump, code"

jump, code

🚀 Common Use Cases

• Numeric thresholds — keep scores above a minimum or prices within a budget.
• Index-based slicing — select items after a header row or skip the first N entries with i > N.
• Blacklist filtering — remove banned IDs, stop words, or duplicate markers from a list.
• Inverted rules — use the third argument when “everything except X” is simpler to write as a positive test plus invert.
• Chained cleanup — pipe several grep passes to progressively narrow results.
• Legacy jQuery codebases — consistent filtering before native Array.filter was widely available.

📝 Notes

• Available since jQuery 1.0 — one of the oldest jQuery utilities.
• The callback must return an explicit boolean; truthy numbers or strings still work in JavaScript but explicit true/false is clearer.
• Inside the callback, this is the global object — not the current array element.
• Only array-like collections are supported; plain objects need Object.values() or $.map first.
• Duplicate values in the source array are preserved if each passes the test.
• For transform-and-filter in one step, consider $.map returning null for rejected items.

💡 Best Practices