I have duplicate data into array and I am trying to fetch index of each element using indexOf. but, it always give index of first record
var data = ["a","b","c","d","a",'c',"a"];
var filterData = data.filter(i=>i == "a");
filterData.forEach(element=>{
var index = data.indexOf(element);
console.log(index);
});
// Expected Answer : 0, 4, 6
https://stackblitz.com/edit/typescript-1ttn4m?file=index.ts
How do I get correct index of each element from original array.
You can do this by keeping track of where the previous element was found at. Using that value, you can skip past those elements when finding the next index.
var data = ["a","b","c","d","a",'c',"a"];
var filterData = data.filter(i => i == "a");
var previousIndex = -1;
filterData.forEach(element=>{
var index = data.slice(++previousIndex).indexOf(element);
console.log(index + previousIndex);
previousIndex += index;
});On Array.forEach, The default format is arr.forEach(callback(currentValue [, index [, array]])[, thisArg]).
You can know more on this link
var data = ["a","b","c","d","a",'c',"a"];
data.forEach((element, index) => {
if (element === 'a') {
console.log(index);
}
});
(element, index) => { /* ... */ }