Read character from string in javascript

Examples

Get the first character in a string:

let text = "HELLO WORLD";
let letter = text.charAt(0);

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Get the second character in a string:

let text = "HELLO WORLD";
let letter = text.charAt(1);

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Get the last character in a string:

let text = "HELLO WORLD";
let letter = text.charAt(text.length-1);

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More examples below.

Definition and Usage

The charAt() method returns the character at a specified index (position) in a string.

The index of the first character is 0, the second 1, ...

Syntax

Parameters

Return Value

More Examples

Index out of range returns empty string:

let text = "HELLO WORLD";
let letter = text.charAt(15);

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Default index is 0:

let text = "HELLO WORLD";
let letter = text.charAt();

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Invalid index converts to 0:

let text = "HELLO WORLD";
let letter = text.charAt(3.14);

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Browser Support

charAt() is an ECMAScript1 (ES1) feature.

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

Examples

Extract a substring from text:

let text = "Hello world!";
let result = text.substring(1, 4);

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Start from position 2:

let result = text.substring(2);

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More examples below.

Definition and Usage

The substring() method extracts characters, between two indices (positions), from a string, and returns the substring.

The substring() method extracts characters from start to end (exclusive).

The substring() method does not change the original string.

If start is greater than end, arguments are swapped: (4, 1) = (1, 4).

Start or end values less than 0, are treated as 0.

Syntax

string.substring(start, end)

Parameters

Return Value

More Examples

If start is greater than end, parameters are swapped:

let result = text.substring(4, 1);

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If "start" is less than 0, it will start from index 0:

let result = text.substring(-3);

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Only the first:

let result = text.substring(0, 1);

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Only the last:

let result = text.substring(text.length - 1);

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Browser Support

substring() is an ECMAScript1 (ES1) feature.

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

How to process each letter of text (with benchmarks)

https://jsperf.com/str-for-in-of-foreach-map-2

for

Classic and by far the one with the most performance. You should go with this one if you are planning to use it in a performance critical algorithm, or that it requires the maximum compatibility with browser versions.

for (var i = 0; i < str.length; i++) {
  console.info(str[i]);
}

for...of

for...of is the new ES6 for iterator. Supported by most modern browsers. It is visually more appealing and is less prone to typing mistakes. If you are going for this one in a production application, you should be probably using a transpiler like Babel.

let result = '';
for (let letter of str) {
  result += letter;
}

forEach

Functional approach. Airbnb approved. The biggest downside of doing it this way is the split(), that creates a new array to store each individual letter of the string.

Why? This enforces our immutable rule. Dealing with pure functions that return values is easier to reason about than side effects.

// ES6 version.
let result = '';
str.split('').forEach(letter => {
  result += letter;
});

or

var result = '';
str.split('').forEach(function(letter) {
  result += letter;
});

The following are the ones I dislike.

for...in

Unlike for...of, you get the letter index instead of the letter. It performs pretty badly.

var result = '';
for (var letterIndex in str) {
  result += str[letterIndex];
}

map

Function approach, which is good. However, map isn't meant to be used for that. It should be used when needing to change the values inside an array, which is not the case.

// ES6 version.
var result = '';
str.split('').map(letter => {
  result += letter;
});

or

let result = '';
str.split('').map(function(letter) {
  result += letter;
});

How do you get a specific letter from a string JavaScript?

How do you access characters in a string?

What is use of charAt () method?

How do you get a specific index of a string in JavaScript?