# Optimization of repetitive operations in JavaScript

Often, novice programmers thoughtlessly call the same function several times, wasting resources.

Let's look at an example. Let's say we have a string containing some path:

`let path = 'img.png';`

Suppose we are faced with the task of checking whether the path ends with the extension `.png` or `.jpg`. Some novice programmer wrote the following code:

`let path = 'img.png'; if (path.slice(-4) === '.png' || path.slice(-4) === '.jpg') { console.log('+++'); } else { console.log('---'); }`

What is wrong with this solution? The problem is that the `slice` method is called twice, doing the same thing. This is, of course, not optimal.

To optimize, you need to slice the string once, write the result into a variable, and then use this variable further:

`let path = 'img.png'; let ext = path.slice(-4); if (ext === '.png' || ext === '.jpg') { console.log('+++'); } else { console.log('---'); }`

Optimize the code below:

`let num = 123; if (String(num)[0] === '1' || String(num)[0] === '2') { console.log('+++'); } else { console.log('---'); }`

Optimize the code below:

`let date = new Date(); if (date.getDay() === 0 || date.getDay() === 6) { console.log('weekend'); } else { console.log('weekday'); }`

Optimize the code below:

`let date = new Date(); let res; if (date.getFullYear() >= 2020 && date.getFullYear() <= 2030) { res = date.getFullYear() + ' fits'; } else { res = date.getFullYear() + ' doesn't fit'; } console.log(res)`
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