大写名称 - 改变原始数组

Question

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.

Answer 1

这将完成工作

let capitaliseNames = (arr) => { arr.forEach((elem, i) => { arr[i] = elem[0].toUpperCase() + elem.slice(1).toLowerCase() }); };

Answer 2

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)

Answer 3

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);

Answer 4

Had a go using the for loop and this works:

let capitaliseNames = (arr) => {
    for (let i = 0; i < arr.length; i++) {
        arr[i] = arr[i][0].toUpperCase() + arr[i].slice(1).toLowerCase();
    }
}