Overwrite Array Values in Javascript

Question

Consider the array variable below...

var fruits = [];
fruits.push("banana");
fruits.push("apple");
fruits.push("mango");
fruits.push("orange");
fruits.push("grapes");

We should have these values...

fruits[0]=>"banana"
fruits[1]=>"apple"
fruits[2]=>"mango"
fruits[3]=>"orange"
fruits[4]=>"grapes"

Say I have a pointer and it's currently at number 2, so the current value is mango, how do I overwrite orange and grapes when I do another push? Is it possible? Say I wanted to add coconut but I don't want it assigned to fruits[5], what I would like to have is orange getting replaced with coconut and it goes on and on... How do I achieve this? Thank you.

you are looking for .splice()

Sheraff
– Sheraff

2020-06-09 15:34:07 +00:00
Commented Jun 9, 2020 at 15:34 — Sheraff
– Sheraff, Commented Jun 9, 2020 at 15:34

inorganik · Accepted Answer · 2020-06-09 15:35:24Z

3

Use splice:

fruits.splice(3, 1, 'coconut')

The arguments are:

start at index
delete count
replace with (optional)

answered Jun 9, 2020 at 15:35

inorganik

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Comments

Jacob · Accepted Answer · 2020-06-09 15:37:57Z

2

Use assignment to replace an item at one index:

fruits[3] = 'coconut';

...or if you don't know where it is:

fruits[fruits.indexOf('orange')] = 'coconut';

Alternatively, if you want to do a replacement with a predicate:

fruits = fruits.map(f => f === 'orange' ? 'coconut' : f);

...or use splice like @inorganik recommended if you want to do more advanced things like replacing a range of indexes with 0 or more replacements.

Lots of options. MDN is a great resource if you have a data type and want to see all the operations available. Here's some Array documentation

answered Jun 9, 2020 at 15:37

Jacob

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Comments

Samuli Hakoniemi · Accepted Answer · 2020-06-09 15:47:49Z

1

There's already a good answer of using splice, I do not mean to disrespect it. However, splice is a method that mutates an existing array. Personally I'd prefer of using slice instead:

const newFruits = fruits.slice(0, end).concat(values);

Where end stands for the "pointer" mentioned in the question. And values represent an array of values to be added (like ['coconut']).

answered Jun 9, 2020 at 15:47

Samuli Hakoniemi

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Comments

Carsten Massmann · Accepted Answer · 2020-06-09 15:49:58Z

1

You could even define your own "psh()" function to start inserting at an arbitrary position like this:

fruits=["banana","apple","mango","orange","grapes"];
function defpsh(arr,i){arr.psh=function(v){ this[i++]=v }}

defpsh(fruits,2); // start "pshing"at offset 2

fruits.psh('coconut');
fruits.psh('lemon');

console.log(fruits);

answered Jun 9, 2020 at 15:49

Carsten Massmann

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