Javascript Inbuilt methods: Part II

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String Data Type: In this chapter we will look into inbuilt methods for string data type.

  • lowercase,
  • uppercase,
  • search,
  • replace,
  • match,
  • trim
  • indexOf
  • substring
  • charAt

1 toLowerCase(): The method converts given string into lowercase.

const sentence = 'The quick brown fox jumps over the lazy dog.'; 

console.log(sentence.toLowerCase());  

2 toUpperCase(): The method converts given string into uppercase.

const sentence = 'The quick brown fox jumps over the lazy dog.'; 

console.log(sentence.toUpperCase());

3 search(): The method executes a search for a match between a regular expression and given string object.

const para = 'The quick brown fox jumps over the lazy dog. If the dog barked, was it really lazy?'; 

const regex = /[^\w\s]/g; console.log(para.search(regex)); 

console.log(para[para.search(regex)]);

4 replace(): The method search and replaces the word from given string.

const para = 'The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?'; 

const regex = /dog/gi; console.log(para.replace(regex, 'ferret')); 

console.log(para.replace('dog', 'monkey'));

5 match(): The method retrieves the result of matching a string against a regular expression.

const para = 'The quick brown fox jumps over the lazy dog. It barked.';  

const regex = /[A-Z]/g; const found = para.match(regex);

6 trim(): The method removes whitespace from both ends of a string.

const greeting = '   Hello world!   '; 

console.log(greeting); 

// expected output: "   Hello world!   ";

7 indexOf(): The method returns the index within the given string of the first occurrence of the specified value, starting the search at from Index. returns -1 if the value is not found.

const para = 'The quick brown fox jumps over the lazy dog. If the dog barked, was it really lazy?';

const searchTerm = 'dog';

const indexOfFirst = para.indexOf(searchTerm);

console.log('The index of the first "' + searchTerm + '" from the beginning is ' + indexOfFirst);

//expected output: "The index of the first "dog" from the beginning is 40"

console.log('The index of the 2nd "' + searchTerm + '" is ' + para.indexOf(searchTerm, (indexOfFirst + 1)));

// expected output: "The index of the 2nd "dog" is 52"

8 substring(): The method returns the part of the string between the start and end indexes, or to the end of the string.

const str = 'Mozilla';

console.log(str.substring(1, 3));

// expected output: "oz"

9 charAt: The String object’s charAt() method returns character at specified index form string.

const sentence = 'The quick brown fox jumps over the lazy dog.';  

const index = 4;  

console.log('The character at index ' + index + ' is ' + 

sentence.charAt(index));  

// expected output: "The character at index 4 is q"