I have the following array:
const people = [
"JoHn", "ChrISTiana", "anThoNY", "MARia", "jaMeS", "MIChaEl", "jeNNIFeR"
];
I want to capitalise the first letter of each word and lowercase the rest.
I have used the following function to generate a new array:
let capitaliseNames = (arr) => {
return arr.map((item) => item[0].toUpperCase() + item.slice(1).toLowerCase());
};
But how do I mutate the original array? I have tried the same approach but using forEach and it doesn't seem to work.
This will do the work
let capitaliseNames = (arr) => { arr.forEach((elem, i) => { arr[i] = elem[0].toUpperCase() + elem.slice(1).toLowerCase() }); };
First: toLowerCase() then you can use a custom function for the mutation the first letter.
UPDATE Use a loop where you can manipulate the original array. For example a for loop.
const people = ["JoHn", "ChrISTiana", "anThoNY", "MARia", "jaMeS", "MIChaEl", "jeNNIFeR"];
for(let i = 0; i < people.length; i++) {
people[i] = capitalizeFirstLetter( people[i].toLowerCase() ) ;
}
function capitalizeFirstLetter(str) {
return str[0].toUpperCase() + str.slice(1);
}
console.log(people)Use forEach() instead of map() and reassign the mutated value back to the original array:
const people = ["JoHn", "ChrISTiana", "anThoNY", "MARia",
"jaMeS", "MIChaEl", "jeNNIFeR"];
const capitaliseNames = (arr) => arr.forEach(
(v, i, a) => a[i] = v[0].toUpperCase() + v.slice(1).toLowerCase()
);
capitaliseNames(people);
console.log(people);