Indexof javascript

This is an array method. Indexof method finds an index of a specific value in an array. If the array has multiple duplicate values then indexof method returns the index of the first value match. It returns '1' if the value matched otherwise it will return '-1'.

1) If the array contains unique values.

1let arr =[1,2,3,4,5]
2  let index = arr.indexOf(3);
3  console.log(index) // 2

In the above example, indexOf finds the index of value '3' and returns it.

2) If the array doesn't contain unique values.

1let arr = [1, 2, 3, 4, 3, 5];
2  let index = arr.indexOf(3);
3  console.log(index); //2

In the above example,'3' is repeated two times but indexOf finds the index of first '3' and which is two (2)

3) Use of indexOf in string

1let arr = 'Hello i am Hassan';
2  let index = arr.indexOf('am');
3  console.log(index); //8

Here we are searing keyword 'am' which starts from index 8

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