Concatenating a string in a forEach loop js-CodePudding

I’m trying some tester code I turn a string into UpperCase Then split it to make it into an array and then loop through it using ES6 forEach loop However when I try to concatenate ‘hello’ to the subject of the loop It returns undefined

const string = 'abcd'
console.log(string.toUpperCase().split('').forEach(element => element  = 'hello'))

And when I add join(‘’) to it it returns this

undefined is not an object (evaluating string.toLowerCase().split('').forEach(element => element  =('hello')).join')

CodePudding user response：

You need to use map function to make any changes to array elements

const string = 'abcd';

console.log(
  string
    .toUpperCase()
    .split('')
    .map(char =>
      char  = ' hello'
    ).join(', ')
);

CodePudding user response：

map is the proper way to do it, but if you need to use forEach, use it like that:

const string = 'abcd'
var newstr = '';
string.toUpperCase().split('').forEach(element => newstr  = element   'hello');
console.log(newstr);