Removing Array Item by Value

How to remove item from array by value?

This can be a global function or a method of a custom object, if you aren't allowed to add to native prototypes. It removes all of the items from the array that match any of the arguments.

Array.prototype.remove = function() {
    var what, a = arguments, L = a.length, ax;
    while (L && this.length) {
        what = a[--L];
        while ((ax = this.indexOf(what)) !== -1) {
            this.splice(ax, 1);
        }
    }
    return this;
};

var ary = ['three', 'seven', 'eleven'];

ary.remove('seven');

/*  returned value: (Array)
three,eleven
*/

To make it a global-

function removeA(arr) {
    var what, a = arguments, L = a.length, ax;
    while (L > 1 && arr.length) {
        what = a[--L];
        while ((ax= arr.indexOf(what)) !== -1) {
            arr.splice(ax, 1);
        }
    }
    return arr;
}
var ary = ['three', 'seven', 'eleven'];
removeA(ary, 'seven');

/*  returned value: (Array)
three,eleven
*/

And to take care of IE8 and below-

if(!Array.prototype.indexOf) {
    Array.prototype.indexOf = function(what, i) {
        i = i || 0;
        var L = this.length;
        while (i < L) {
            if(this[i] === what) return i;
            ++i;
        }
        return -1;
    };
}

How can I remove a specific item from an array?

Find the index of the array element you want to remove using indexOf, and then remove that index with splice.

The splice() method changes the contents of an array by removing
existing elements and/or adding new elements.

const array = [2, 5, 9];

console.log(array);

const index = array.indexOf(5);
if (index > -1) { // only splice array when item is found
  array.splice(index, 1); // 2nd parameter means remove one item only
}

// array = [2, 9]
console.log(array); 

The best way to remove array element by value

Here's how it's done:

var arr = ["orange","red","black","white"];
var index = arr.indexOf("red");
if (index >= 0) {
  arr.splice( index, 1 );
}

This code will remove 1 occurency of "red" in your Array.

PHP array delete by value (not key)

Using array_search() and unset, try the following:

if (($key = array_search($del_val, $messages)) !== false) {
    unset($messages[$key]);
}

array_search() returns the key of the element it finds, which can be used to remove that element from the original array using unset(). It will return FALSE on failure, however it can return a false-y value on success (your key may be 0 for example), which is why the strict comparison !== operator is used.

The if() statement will check whether array_search() returned a value, and will only perform an action if it did.

Remove array element based on object property

One possibility:

myArray = myArray.filter(function( obj ) {
    return obj.field !== 'money';
});

Please note that filter creates a new array. Any other variables referring to the original array would not get the filtered data although you update your original variable myArray with the new reference. Use with caution.

How to delete an item from state array?

To remove an element from an array, just do:

array.splice(index, 1);

In your case:

removePeople(e) {
  var array = [...this.state.people]; // make a separate copy of the array
  var index = array.indexOf(e.target.value)
  if (index !== -1) {
    array.splice(index, 1);
    this.setState({people: array});
  }
},

How do I remove an array item in TypeScript?

Same way as you would in JavaScript.

delete myArray[key];

Note that this sets the element to undefined.

Better to use the Array.prototype.splice function:

const index = myArray.indexOf(key, 0);
if (index > -1) {
   myArray.splice(index, 1);
}

Remove Object from Array using JavaScript

You can use several methods to remove item(s) from an Array:

//1
someArray.shift(); // first element removed
//2
someArray = someArray.slice(1); // first element removed
//3
someArray.splice(0, 1); // first element removed
//4
someArray.pop(); // last element removed
//5
someArray = someArray.slice(0, someArray.length - 1); // last element removed
//6
someArray.length = someArray.length - 1; // last element removed

If you want to remove element at position x, use:

someArray.splice(x, 1);

Or

someArray = someArray.slice(0, x).concat(someArray.slice(-x));

Reply to the comment of @chill182: you can remove one or more elements from an array using Array.filter, or Array.splice combined with Array.findIndex (see MDN).

See this Stackblitz project or the snippet below:

// non destructive filter > noJohn = John removed, but someArray will not change
let someArray = getArray();
let noJohn = someArray.filter( el => el.name !== "John" ); 
log(`let noJohn = someArray.filter( el => el.name !== "John")`,
  `non destructive filter [noJohn] =`, format(noJohn));
log(`**someArray.length ${someArray.length}`);

// destructive filter/reassign John removed > someArray2 =
let someArray2 = getArray();
someArray2 = someArray2.filter( el => el.name !== "John" );
log("", 
  `someArray2 = someArray2.filter( el => el.name !== "John" )`,
  `destructive filter/reassign John removed [someArray2] =`, 
  format(someArray2));
log(`**someArray2.length after filter ${someArray2.length}`);

// destructive splice /w findIndex Brian remains > someArray3 =
let someArray3 = getArray();
someArray3.splice(someArray3.findIndex(v => v.name === "Kristian"), 1);
someArray3.splice(someArray3.findIndex(v => v.name === "John"), 1);
log("",
  `someArray3.splice(someArray3.findIndex(v => v.name === "Kristian"), 1),`,
  `destructive splice /w findIndex Brian remains [someArray3] =`, 
  format(someArray3));
log(`**someArray3.length after splice ${someArray3.length}`);

// if you're not sure about the contents of your array, 
// you should check the results of findIndex first
let someArray4 = getArray();
const indx = someArray4.findIndex(v => v.name === "Michael");
someArray4.splice(indx, indx >= 0 ? 1 : 0);
log("", `someArray4.splice(indx, indx >= 0 ? 1 : 0)`,
  `check findIndex result first [someArray4] = (nothing is removed)`,
  format(someArray4));
log(`**someArray4.length (should still be 3) ${someArray4.length}`);

// -- helpers -- 
function format(obj) {
  return JSON.stringify(obj, null, " ");
}

function log(...txt) {
  document.querySelector("pre").textContent += `${txt.join("\n")}\n`
}

function getArray() {
  return [ {name: "Kristian", lines: "2,5,10"},
           {name: "John", lines: "1,19,26,96"},
           {name: "Brian", lines: "3,9,62,36"} ];
}

<pre>
**Results**

</pre>

javascript - remove array element on condition

You could add your own method to Array that does something similar, if filter does not work for you.

Array.prototype.removeIf = function(callback) {
    var i = 0;
    while (i < this.length) {
        if (callback(this[i], i)) {
            this.splice(i, 1);
        }
        else {
            ++i;
        }
    }
};

To me, that's one of the coolest features of JavaScript. Ian pointed out a more efficient way to do the same thing. Considering that it's JavaScript, every bit helps:

Array.prototype.removeIf = function(callback) {
    var i = this.length;
    while (i--) {
        if (callback(this[i], i)) {
            this.splice(i, 1);
        }
    }
};

This avoids the need to even worry about the updating length or catching the next item, as you work your way left rather than right.

remove objects from array by object property

I assume you used splice something like this?

for (var i = 0; i < arrayOfObjects.length; i++) {
    var obj = arrayOfObjects[i];

    if (listToDelete.indexOf(obj.id) !== -1) {
        arrayOfObjects.splice(i, 1);
    }
}

All you need to do to fix the bug is decrement i for the next time around, then (and looping backwards is also an option):

for (var i = 0; i < arrayOfObjects.length; i++) {
    var obj = arrayOfObjects[i];

    if (listToDelete.indexOf(obj.id) !== -1) {
        arrayOfObjects.splice(i, 1);
        i--;
    }
}

To avoid linear-time deletions, you can write array elements you want to keep over the array:

var end = 0;

for (var i = 0; i < arrayOfObjects.length; i++) {
    var obj = arrayOfObjects[i];

    if (listToDelete.indexOf(obj.id) === -1) {
        arrayOfObjects[end++] = obj;
    }
}

arrayOfObjects.length = end;

and to avoid linear-time lookups in a modern runtime, you can use a hash set:

const setToDelete = new Set(listToDelete);
let end = 0;

for (let i = 0; i < arrayOfObjects.length; i++) {
    const obj = arrayOfObjects[i];

    if (setToDelete.has(obj.id)) {
        arrayOfObjects[end++] = obj;
    }
}

arrayOfObjects.length = end;

which can be wrapped up in a nice function:

const filterInPlace = (array, predicate) => {

    let end = 0;

    for (let i = 0; i < array.length; i++) {

        const obj = array[i];

        if (predicate(obj)) {

            array[end++] = obj;

        }

    }

    array.length = end;

};

const toDelete = new Set(['abc', 'efg']);

const arrayOfObjects = [{id: 'abc', name: 'oh'},

                        {id: 'efg', name: 'em'},

                        {id: 'hij', name: 'ge'}];

filterInPlace(arrayOfObjects, obj => !toDelete.has(obj.id));

console.log(arrayOfObjects);

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