How to flat array but to take only first index ? Js-CodePudding

I need to flat arrays but i can't to use flat().

First check example of my arrays

let arr = [
 ['test1' , 'test1'],
 ['test2' , 'test2'],
 ['test3', true],
 ['test4' , false]
];

What is problem here?

I need to get only first item 'test1' , 'test2', 'test3', 'test4' and push to one array

After that I want to my array be;

['test1' , 'test2' , 'test3' , 'test4' ];

What I'm try:

let arr = [
 ['test1' , 'test1'],
 ['test2' , 'test2'],
 ['test3', true],
 ['test4' , false]
];

let newArr = arr.flat();

but I got all items not first index in each array

CodePudding user response：

Using Array#map:

const arr = [ ['test1' , 'test1'], ['test2' , 'test2'], ['test3', true], ['test4' , false] ];

const res = arr.map(([ e ]) => e);

console.log(res);

CodePudding user response：

You need to use Array.map() first,then invoke Array.flat()

let arr = [
 ['test1' , 'test1'],
 ['test2' , 'test2'],
 ['test3', true],
 ['test4' , false]
];

let result = arr.map(i => i[0]).flat()
console.log(result)

CodePudding user response：

Try this :

let arr = [
 ['test1' , 'test1'],
 ['test2' , 'test2'],
 ['test3', true],
 ['test4' , false]
];

console.log(arr.map(innerArr => innerArr[0]));