use array index to find value code example
Example 1: how to find the index of a value in an array in javascript
var list = ["apple","banana","orange"]
var index_of_apple = list.indexOf("apple") // 0
Example 2: index of value in array
// for dictionary case use findIndex
var imageList = [
{value: 100},
{value: 200},
{value: 300},
{value: 400},
{value: 500}
];
var index = imageList.findIndex(img => img.value === 200);