10 javascript string methods you should know

Sun, 8 July 2018
3 min read

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

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(' ')); // true
    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)); // ''