Javascript text value length

String: length

The length data property of a String value contains the length of the string in UTF-16 code units.

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Value

Property attributes of String: length
Writable	no
Enumerable	no
Configurable	no

Description

This property returns the number of code units in the string. JavaScript uses UTF-16 encoding, where each Unicode character may be encoded as one or two code units, so it’s possible for the value returned by length to not match the actual number of Unicode characters in the string. For common scripts like Latin, Cyrillic, wellknown CJK characters, etc., this should not be an issue, but if you are working with certain scripts, such as emojis, mathematical symbols, or obscure Chinese characters, you may need to account for the difference between code units and characters.

The language specification requires strings to have a maximum length of 2 53 — 1 elements, which is the upper limit for precise integers. However, a string with this length needs 16384TiB of storage, which cannot fit in any reasonable device’s memory, so implementations tend to lower the threshold, which allows the string’s length to be conveniently stored in a 32-bit integer.

• In V8 (used by Chrome and Node), the maximum length is 2 29 — 24 (~1GiB). On 32-bit systems, the maximum length is 2 28 — 16 (~512MiB).
• In Firefox, the maximum length is 2 30 — 2 (~2GiB). Before Firefox 65, the maximum length was 2 28 — 1 (~512MiB).
• In Safari, the maximum length is 2 31 — 1 (~4GiB).

For an empty string, length is 0.

The static property String.length is unrelated to the length of strings. It’s the arity of the String function (loosely, the number of formal parameters it has), which is 1.

Since length counts code units instead of characters, if you want to get the number of characters, you can first split the string with its iterator, which iterates by characters:

function getCharacterLength(str)  // The string iterator that is used here iterates over characters, // not mere code units return [. str].length; > console.log(getCharacterLength("A\uD87E\uDC04Z")); // 3 

Examples

Basic usage

const x = "Mozilla"; const empty = ""; console.log(`$x> is $x.length> code units long`); // Mozilla is 7 code units long console.log(`The empty string has a length of $empty.length>`); // The empty string has a length of 0 

Strings with length not equal to the number of characters

const emoji = "😄"; console.log(emoji.length); // 2 console.log([. emoji].length); // 1 const adlam = "𞤲𞥋𞤣𞤫"; console.log(adlam.length); // 8 console.log([. adlam].length); // 4 const formula = "∀𝑥∈ℝ,𝑥²≥0"; console.log(formula.length); // 11 console.log([. formula].length); // 9 

Assigning to length

Because string is a primitive, attempting to assign a value to a string’s length property has no observable effect, and will throw in strict mode.

const myString = "bluebells"; myString.length = 4; console.log(myString); // "bluebells" console.log(myString.length); // 9 

Specifications

Browser compatibility

BCD tables only load in the browser

See also

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JavaScript String length

ES1 (JavaScript 1997) is fully supported in all browsers:

Chrome	Edge	Firefox	Safari	Opera	IE
Yes	Yes	Yes	Yes	Yes	Yes

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Get Input Value Length in JavaScript

In this tutorial we will learn how to Get Input Value Length in JavaScript. HTML DOM getElementById() method, JavaScript length property and JavaScript value property is used for this purpose.

HTML Code

HTML Code is given below, in this code we have a input tag and a button tag with onclick event which will execute a JavaScript function to get the length of the value inside the input element.

JavaScript Code

Take a look at the JavaScript code, the HTML Dom getElementById() method, length property and value property is used.

getElementById() Method

getElementById() Method is used to select element with the specified id.

JavaScript value property

JavaScript value property is used to set or get the value of the selected HTML element.

JavaScript length property

JavaScript length property is used to get the length of the string. In this example it will return the length of the value of input element.

Demo

Video Tutorial

Watch video tutorial on Get Input Value Length in JavaScript.

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