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10 javascript string methods you should know

Frugence | 3 years ago

In this post I will summarize 10 javascript string methods you should at least known.

If interested read here 10 javascript array methods you should know.

String is anything inside single or double quotes.

Here are 10 javascript string methods you should know.

1. startsWith()
Check if string starts with specified character(s).
  const str = 'JavaScript is amazing';

  console.log(str.startsWith('JavaScript')); // true
  console.log(str.startsWith('Java')); // true
  console.log(str.startsWith('javascript')); // false

  // position is optional
  // if not specified, the default value is 0
  console.log(str.startsWith('Script', 4)); // true
  console.log(str.startsWith('SCRIPT', 4)); // false
2. endsWith()
Check if string ends with specified character(s).
  const str = 'JavaScript is amazing';

  // check if ends with 'amazing'
  console.log(str.endsWith('amazing')); // true
  console.log(str.endsWith('ing')); // true
  console.log(str.endsWith('Amazing')); // false

  // length is optional
  // if not specified, the default value is length of the string
  console.log(str.endsWith('is', 13)); // true
  console.log(str.endsWith('i', 13)); // false
  console.log(str.endsWith('s', 13)); // true
3. includes()
Check if string contains specified character(s).
  const str = 'JavaScript is amazing';

  console.log(str.includes('Script')); // true
  console.log(str.includes('script')); // false
  console.log(str.includes('array')); // false
4. slice()
Copy some part of string without modifying the original one.
  const str = 'JavaScript is amazing';

  // Default start index is 0
  console.log(str.slice()); // 'JavaScript is amazing'

  // start copy at index 4
  console.log(str.slice(4)); // 'Script is amazing'

  // end copy at index 10(character at this index will not be included)
  console.log(str.slice(0, 10)); // 'JavaScript'
5. toUpperCase()
Convert string into upper case.
  const str = 'JavaScript is amazing';

  console.log(str.toUpperCase()); // 'JAVASCRIPT IS AMAZING'
6. toLowerCase()
Convert string into lower case.
  const str = 'JavaScript is amazing';

  console.log(str.toLowerCase()); // 'javascript is amazing'
7. charAt()
Return character at specified position.
  const str = 'JavaScript is amazing';

  console.log(str.charAt()); // 'J'
  console.log(str.charAt(11)); // 'i'
  console.log(str.charAt(14)); // 'a'
  console.log(str.charAt(110)); // ''
8. split()
Split string into array of substrings.
  const str = 'JavaScript is amazing';
  const strNew = 'JavaScript-is-amazing';

  console.log(str.split()); // ["JavaScript is amazing"]

  // Separator string used to determine where to make each split
  console.log(str.split('S')); // ["Java", "cript is amazing"]
  console.log(str.split('is')); // ["JavaScript ", " amazing"]
  console.log(str.split(' ')); // ["JavaScript", "is", "amazing"]
  console.log(strNew.split('-')); // ["JavaScript", "is", "amazing"]
9. replace()
Replaces specified value with another value in a string.
  const str = 'JavaScript is amazing';

  console.log(str.replace('JavaScript', 'Node.js')); // 'Node.js is amazing'

  // replace() method is case sensitive
  // replace will not work
  console.log(str.replace('Javascript', 'Node.js')); // 'JavaScript is amazing'

  // use regular expression for case insensitive
  console.log(str.replace(/Javascript/i, 'Node.js')); // 'Node.js is amazing'

  // replace() method replaces only the first match
  console.log(str.replace('a', 'A')); // 'JAvaScript is amazing'

  // to replace all matches, use regular expression
  console.log(str.replace(/a/g, 'A')); // 'JAvAScript is AmAzing'
10. repeat()
Return new string with specified number of copies of existing string.
  const str = 'JavaScript';

  console.log(str.repeat(3)); // 'JavaScriptJavaScriptJavaScript'
  console.log(str.repeat(1)); // 'JavaScript'
  console.log(str.repeat(0)); // ''