I want to cycle through an array of numbers and if any of those numbers are single digit add a 0 before it, eg 1 becomes 01.
I could do this with a for loop but was wondering if I could use forEach as it seems neater.
Would anyone know if this can be done?
My code so far:
numArr.forEach(function(item) {
if (item < 10) {
item = '0' + item; // How do I update this value in array?
}
});
You pass index as the second parameter to event handler function and use that index to modify the item in array:
numArr.forEach(function(item, i) {
if (item < 10) {
numArr[i] = '0' + item; // How do I update this value in array?
}
});
You can also use map():
numArr = numArr.map(function(item, i) => {
if (item < 10) {
item = '0' + item; // How do I update this value in array?
}
return item;
});
0 + item converts the value to number
You could map the array with Array#map and convert the value to string and pad with a wanted length and value.
var numArr = [1, 2, 3, 10],
zeroes = numArr.map(v => v.toString().padStart(2, '0'));
console.log(zeroes);If you want to modify your array in place, then Array.forEach() is the way to go and you'll have to use the index for that, which is the second argument of your callback.
However, if you want to generate a new array, I suggest using Array.map() which returns a new item for each iteration:
const numArr = [-1, 0, 1, 2, 3, 10, 11, 12, 100, 3.14];
const prefix = x => {
const s = `0${x.toString().replace('-', '')}`;
return s.split('.')[0].length >= 3 ? `${x}` : `${x < 0 ? '-' : ''}${s}`;
}
const result = numArr.map(prefix);
numArr.forEach((x, i) => numArr[i] = prefix(x));
console.log(result);
console.log(numArr);You can use map,
var numArr = [1, 2, 3,10,11];
numArr = numArr.map(function(item) {
if (item < 10) {
return item = '0' + item;;
}
return item.toString() ;
});
console.log(numArr);One more oprtion is to use forEach with two parameters(second parameter will be index),
var numArr = [1, 2, 3,10,11];
numArr.forEach(function(item,index) {
if (item < 10) {
numArr[index] = '0' + item;
}
});
console.log(numArr);
var cont = [1, 2, 3, 4, 5, 6, 7, 10, 11, 12];
var result = cont.map((o)=>{ return o.toString().padStart('2', 0);});
console.log(result);
mapfunction is more appropriate for this.String#padStart.