How to remove element from array using javascript

Question

I have 2 array and want to remove the elements of 2nd array as per position numbers on 1st array.

var notexists = []; //value is "1","5","8" on 0,1,2nd position. 
var copyrequiredfields = [];//Value is "a","b","c","d","e","f",...
for (var i = 0; i < notexists.length; i++) {
     copyrequiredfields.splice(parseInt(notexists[i]), 1);
}

as per example i want to remove 1st 5th and 8th element from copyrequiredfields . Please suggest some answer.

There are probably a lot of ways to do this. Could you give more detail on what the overall goal is you are trying to achieve? It would be easier to suggest a solution if we knew why you wanted to do this. — John Halbert
– John Halbert, Commented Oct 8, 2016 at 5:35
Use slice if you're basing the results on position. Of course, slice does not affect the initial array, like splice does. Note that splice takes a count, not a position. — StackSlave
– StackSlave, Commented Oct 8, 2016 at 5:35
@chhaya_patel I have added answer with both array.splice and array.filter. Hope it helps! — Rajesh Dixit
– Rajesh Dixit, Commented Oct 8, 2016 at 5:54

Rong Zhao · Accepted Answer · 2016-10-08 05:39:31Z

1

Create a new array, iterate the copyrequiredfields, when the index in notexists, ignore it.

example:

var notexist = [1,2,5];
var copyrequiredfields = ['a','b','c','d','e','f','g'];
//create a index map
var index_map = {};
for(var i = 0; i < notexist.length; i++){
    index_map[notexist[i]] = true;
}
//remove the elements
var newarray = [];
for(var i = 0; i < copyrequiredfields.length; i++){
    if(!index_map[i]){
        newarray.push(copyrequiredfields[i]);
    }
}
copyrequiredfields = newarray;

answered Oct 8, 2016 at 5:39

Rong Zhao

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Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

In JS, index of array starts with 0 and not 1 so you just have to subtract 1 from value before splice. Rest of the code is fine.

One issue is, as you remove elements from array, elements after it are moved 1 position back. This will give you incorrect output. 1 hack is to count number of elements removed to count movement.

A better solution would be to use array.filter.

Array.splice

var notexists = ["1", "5", "8"]; //value is  on 0,1,2nd position. 
var copyrequiredfields = ["a", "b", "c", "d", "e", "f", "g", "h", "i"]; //Value is "a","b","c","d","e","f",...
var count=0;
for (var i = 0; i < notexists.length; i++) {
  console.log(+notexists[i] - 1)
  copyrequiredfields.splice(+notexists[i]-1-count++, 1);
}

console.log(copyrequiredfields)

Array.filter

var notexists = ["1", "5", "8"]; //value is  on 0,1,2nd position. 
var copyrequiredfields = ["a", "b", "c", "d", "e", "f", "g", "h", "i"]; //Value is "a","b","c","d","e","f",...
var r = copyrequiredfields.filter((x,i)=>notexists.indexOf((i+1).toString()) === -1)
console.log(r)

Syntac · Accepted Answer · 2016-10-08 05:40:57Z

0

You could copy the whole array, except of the parts you dont need anymore:

var tempCopy = [];
for (var i=0; i < copyrequiredfields.length; i++)
    if(notexists.indexOf(i)==-1)
        tempCopy.push(copyrequiredfields[i]);
copyrequiredfields = tempCopy;

Greets!

answered Oct 8, 2016 at 5:40

Syntac

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