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What do square brackets mean in js

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Square brackets are used for arrays in JavaScript. An array is an ordered data structure used to store a sequence of values. Square brackets have two main uses: one is to access array elements by element index, and the other is to modify array elements.

What do square brackets mean in js

The meaning of square brackets in JavaScript

square brackets, that is, [ and ], is mainly used to represent arrays in JavaScript. An array is an ordered data structure used to store a sequence of values.

The syntax of square brackets

<code class="javascript">const array = [element1, element2, ..., elementN];</code>

Where:

  • array is the name of the array.
  • Square brackets are used to define the boundaries of the array.
  • element1, element2, ..., elementN are the values ​​stored in the array.
  • Separate elements with commas.

Use of square brackets

Square brackets have two main uses:

1. Access array elements

We can access specific elements in an array using square brackets and element index. Indexing starts at 0, which represents the first element in the array. For example:

<code class="javascript">const array = [1, 2, 3, 4, 5];
console.log(array[2]); // 输出:3</code>

2. Modify array elements

You can also use square brackets and element indexes to modify elements in the array. For example:

<code class="javascript">const array = [1, 2, 3, 4, 5];
array[2] = 10;
console.log(array); // 输出:[1, 2, 10, 4, 5]</code>

Note:

  • Arrays can contain any type of value, including numbers, strings, objects, and arrays.
  • The length of the array is dynamic and elements can be added or removed at any time.
  • When accessing an element that does not exist, JavaScript will return undefined.

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