I have an array of objects . I need to convert the value of the 'key' by incrementing count .
lets say I have an array
const arr1=[{key:'a', val:1},{key:'b',val:2}]
I want to give an incrementing key value to each key
I have tried the below code but couldn't override the count value
let count = 0;
const arr1=[{key:'a', val:1},{key:'b',val:2}]
arr1.map(el => el.key=count+1);
console.log(arr1)
Expected Result :
[ { key: 1, val: 1 }, { key: 2, val: 2 } ]
You could use forEach to loop through the array and update the key based on the index
const array = [ { key: 1, val: 1 }, { key: 2, val: 2 } ]
array.forEach((o, i) => o.key = i+1)
console.log(array)If you want a new array you could use map like this:
const array = [ { key: 1, val: 1 }, { key: 2, val: 2 } ],
newArray = array.map((o, i) => ({ ...o, key: i+1}));
console.log(newArray)Because it looks like you want to perform side-effects rather than create a new array, use forEach instead of .map. You also need to actually increment the count variable on each iteration:
let count = 0;
const arr1=[{key:'a', val:1},{key:'b',val:2}]
arr1.forEach(el => {
count++;
el.key = count;
});
console.log(arr1)
Use ++ to update count while getting the new value. Also, you need to return the modified el from map, and make sure you assign the return value otherwise it'll be garbage-collected - map returns a new array.
let count = 0;
const arr1 = [{key:'a',val:1},{key:'b',val:2}];
const res = arr1.map(({ val }) => ({ key: ++count, val }));
console.log(res);