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Learn how to use the length property to get or set the number of elements in an array. See examples, syntax, return value, and browser support for this ECMAScript1 feature.
- Js Arrays
The length property of an array returns the length of an...
- Js Arrays
- Overview
- Description
- Examples
- Browser compatibility
- See also
The length data property of an Array instance represents the number of elements in that array. The value is an unsigned, 32-bit integer that is always numerically greater than the highest index in the array.
The value of the length property is a nonnegative integer with a value less than 232.
The array object observes the length property, and automatically syncs the length value with the array's content. This means:
•Setting length to a value smaller than the current length truncates the array — elements beyond the new length are deleted.
•Setting any array index (a nonnegative integer smaller than 232) beyond the current length extends the array — the length property is increased to reflect the new highest index.
•Setting length to an invalid value (e.g. a negative number or a non-integer) throws a RangeError exception.
When length is set to a bigger value than the current length, the array is extended by adding empty slots, not actual undefined values. Empty slots have some special interactions with array methods; see array methods and empty slots.
Iterating over an array
In the following example, the array numbers is iterated through by looking at the length property. The value in each element is then doubled.
Shortening an array
The following example shortens the array numbers to a length of 3 if the current length is greater than 3.
Create empty array of fixed length
Setting length to a value greater than the current length creates a sparse array.
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•Indexed collections guide
•Array
•TypedArray.prototype.length
•String: length
Learn how to use the length property to get the size of an array in JavaScript. See examples, explanations and answers from experts and users on Stack Overflow.
- Because 2 isn't an array, it's a number. Numbers have no length. Perhaps you meant to write testvar.length ; this is also undefined, since objects...
- testvar[1] is the value of that array index, which is the number 2. Numbers don't have a length property, and you're checking for 2.length which is...
- Integer has no method length. Try string var testvar={}; testvar[1]="2"; alert(testvar[1].length);
- If length is undefined you can use: function count(array){ var c = 0; for(i in array) // in returns key, not object if(array[i] != undefin...
- var mode = []; $("input[name='mode[]']:checked").each(function(i) { mode.push($(this).val()); }) if(mode.length == 0)...
- obj={}; $.each(obj, function (key, value) { console.log(key+ ' : ' + value); //push the object value }); for (var i in obj) { nameList += ""...
- var array=[]; array.push(array); //insert the array value using push methods. for (var i = 0; i < array.length; i++) { nameList += "" + array...
Mar 19, 2024 · Learn different approaches to count the elements within an array in JavaScript, such as using the length property, looping, spread operator, and reduce method. See examples, output, and code explanations for each method.
Learn how to use the length property of an array to get or change the number of elements in a dense or sparse array. See code examples and explanations of how the length property works.
The length property of an array returns the length of an array (the number of array elements).
People also ask
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Learn how to use the length property to get or set the number of elements in an array. See examples of finding, changing, and using the length property in loops and operations.
