Let some programmer check if the array
contains the number 3
:
let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
let exists = false;
for (let elem of arr) {
if (elem === 3) {
exists = true;
break;
}
}
console.log(exists);
I claim that there is something wrong with
this code. What is wrong, we exit the loop
after we have found the number 3
? The
fact is that functions built into JavaScript
always work faster than similar self-written
code.
In our case, there is the includes
function that solves the problem, and we
need to use this particular function:
let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
console.log(arr.includes(3));
Moral: Before solving a problem, be sure to check if there is a built-in JavaScript function to solve it.
The following code checks if a string
starts with 'http'
. Perform
optimization:
let str = 'http://learn.itnots.ru';
if (str[0] + str[1] + str[2] + str[3] === 'http') {
console.log('+++');
} else {
console.log('---');
}
The following code populates an array with a given value. Perform optimization:
let arr = fillArr('x', 5);
console.log(arr);
function fillArr(val, amount) {
let arr = [];
for (let i = 1; i <= amount; i++) {
arr.push(val);
}
return arr;
}