Page 120 - JavaScript

[1, 1, 1].every(function(item, i, list) { return item === list[0]; }); // true

6

[1, 1, 1].every((item, i, list) => item === list[0]); // true

The following code snippets test for property equality

let data = [
{ name: "alice", id: 111 },
{ name: "alice", id: 222 }
];

data.every(function(item, i, list) { return item === list[0]; }); // false
data.every(function(item, i, list) { return item.name === list[0].name; }); // true

6

data.every((item, i, list) => item.name === list[0].name); // true

Copy part of an Array

The slice() method returns a copy of a portion of an array.

It takes two parameters, arr.slice([begin[, end]]) :

begin

Zero-based index which is the beginning of extraction.

end

Zero-based index which is the end of extraction, slicing up to this index but it's not included.

If the end is a negative number,end = arr.length + end.

Example 1

// Let's say we have this Array of Alphabets
var arr = ["a", "b", "c", "d"...];

// I want an Array of the first two Alphabets
var newArr = arr.slice(0, 2); // newArr === ["a", "b"]

Example 2

// Let's say we have this Array of Numbers

https://riptutorial.com/ 77