Question

How to find all the occurrences of an element in array with JavaScript

Answer 1

var indexes = [];
var array = ['a', 'b', 'a', 'c', 'd', 'a', 'e', 'a', 'a'];
var element = 'a';
var i = array.lastIndexOf(element);
while (i != -1) 
{
  indexes.push(i);
  i = (i > 0 ? array.lastIndexOf(element, i - 1) : -1);
}

console.log(indexes);

/*
run:

[8, 7, 5, 2, 0]

*/

 

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Answer 2

var indexes = [];
var array = ['a', 'b', 'a', 'c', 'd', 'a', 'e', 'a', 'a'];
var element = 'a';
var i = array.indexOf(element);
while (i != -1) 
{
  indexes.push(i);
  i = (i >= 0 ? array.indexOf(element, i + 1) : -1);
}

console.log(indexes);

/*
run:

[0, 2, 5, 7, 8]

*/

 

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