How do i iterate over a string in javascript?

Question

Looping Through a String

The length Property

The length property has the string length, it simply returns the number of characters in the string:

Nội dung chính Show

Looping Through a String
The length Property
Use the string index number to loop through a string
results matching ""
No results matching ""
Learn about the most popular string-iteration techniques in JavaScript
How to Access a Single Character of a String
Bracket notation
Which method is preferable?
Popular Ways to Iterate Strings
How do I iterate over a string?
How can we iterate through individual words in a string JavaScript?
How do you iterate data in JavaScript?
How do I loop through a string in typescript?

let str = "hello123";
alert(str.length);            // 8

// the last character
alert(str[str.length - 1]);   // 3

Please note that str.length is a numeric property, not a function. There is no need to add brackets after it.

Use the string index number to loop through a string

for loop

To walk over all the characters of a string, we can use an ordinary for loop, with a loop counter (i) to go through string index from 0 to str.length:

// ordinary for loop
let str = "Buzz";
for (let i = 0; i < str.length; i++) {
  console.log(str[i]);
}

for ... in ...

There exists a special form of the loop: for...in.... This is different from the ordinary for loop that we studied before.

In this loop, the variable i automatically receives the index so that each character can be accessed using str[i].

Example:

// for... in
for (let i in str) {
  console.log(str[i]);
}

The above two kinds of for loop will loop through string str just the same, they all give the same result in the console:

B
u
z
z

for ... of ...

Another way to iterate over a string is to use for item of str. The variable item receives the character directly so you do not have to use the index. If your code does not need the index value of each character, this loop format is even simpler.

Example:

// for ... of ...
for (let char of "Hello") {
  console.log(char);
}

// console result:
H
e
l
l
o

results matching ""

No results matching ""

Learn about the most popular string-iteration techniques in JavaScript

Photo by Yurii Stupen on Unsplash

For many things in JavaScript, there’s not a single way to achieve them. A thing as simple as iterating over each character in a string is one of them. Let’s explore some methods and discuss their upsides and downsides.

Before we start, we need to come back to a much more basic question.

How to Access a Single Character of a String

Nowadays with ECMAScript 2015 (ES6), there are two ways of accessing a single character:

charAt()

This method of the string object has been around for some time now and can be seen as the classic approach. It’s supported even in oldest browsers.

Bracket notation

The second method is accessing a character via bracket notation:

This approach has been introduced with ECMAScript 2015 and seems to be more convenient. Furthermore, it allows you to treat a string like an array-like structure. This enables a couple of iteration methods, as we’ll see soon.

Which method is preferable?

A downside of charAt() might be readability. However, it’s compatible with old browsers like IE7. Another argument against bracket notation is it can’t be used for assigning a character:

This can be confusing, especially because there won’t be a warning.

In my personal opinion, bracket notation is more convenient to write and read. Compatibility issues should be solved by transpiling instead of not using the desired feature.

Popular Ways to Iterate Strings

The following list of techniques doesn’t claim to be complete. It’ll show some of the most frequently used approaches.

In order to demonstrate the processing of the single characters of our string, we’ll use the following function:

for loop

The classic approach — a simple for loop:

While a bit cumbersome to write and read, this is the fastest known method.

for…of

This statement was introduced with ECMAScript 2015 and can be used with iterable objects. It’s more convenient to write than a classic for loop if you don’t care about the current index in the loop body.

forEach()

This is the functional version of a for loop. Many people prefer it over for…of and for loops because it’s a higher-order function, and it helps to stick to a programming style that leverages immutability (see the Airbnb style guide in the references).

One downside is you need to convert the string into an array before iterating. If performance really matters in your use case (and it usually doesn’t), it might not be your first choice.

Conclusion

As with many techniques in JavaScript, it’s mainly a matter of taste when deciding which one to use. However, be aware of the speed impacts of the string-to-array conversion as well as the compatibility issues of the bracket notation.

I advise you to pick the most readable technique and only care for speed optimization if you have a performance problem and to solve compatibility issues through transpiling.

How do I iterate over a string?

Iterate over characters of a String in Java.

Naive solution. A naive solution is to use a simple for-loop to process each character of the string. ... .

Using String.toCharArray() method. ... .

Using Iterator. ... .

Using StringTokenizer. ... .

Using String. ... .

Using Guava Library. ... .

Using String.chars() method. ... .

Using Code Points..

How can we iterate through individual words in a string JavaScript?

Simple for loop can use for in iterate through words in a string JavaScript. And for iterate words in string use split, map, and join methods (functions).

How do you iterate data in JavaScript?

There are multiple ways one can iterate over an array in Javascript. The most useful ones are mentioned below. ... .

Using while loop. This is again similar to other languages..

using forEach method. ... .

Using every method. ... .

Using map. ... .

Using Filter..

Using Reduce..

Using Some..

How do I loop through a string in typescript?

To iterate over a string with index: Use the spread syntax (...) to unpack the string into an array. Use the forEach() method to iterate over the array. The second parameter the forEach() method takes is the index of the current element.

programming javascript For ES6 For...in JS For loop array Remove string JavaScript