21 Useful JavaScript Tips That'll Help You Save Time

21 Useful JavaScript Tips That'll Help You Save Time

Suhail Kakar
·Jul 23, 2021·

5 min read

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JavaScript is a programming language used primarily by Web browsers to create a dynamic and interactive experience for the user. Most of the functions and applications that make the Internet indispensable to modern life are coded in some form of JavaScript. While JavaScript is not the only client-side scripting language on the Internet, it was one of the first and it is still the most widely used. Many developers believe that JavaScript is inefficient and finicky, so they have made many improvements to the language over the years.

Here are the 21 JavaScript tricks that makes you a JavaScript pro

  1. Use logical AND / OR for conditions

    var xyz = 23;  
    xyz == 10 && runFunction(); // is the same thing as if (xyz == 23) runFunction(); 
    xyz == 5 || runFunction(); // is the same thing as if (xyz != 23) runFunction();
  2. Avoid using for loop for arrays

    Instead of using
    var add = 10;  
    for (var i in arrayAdd) {  
    add += arrayAdd[i];  
    It is better to use
    var add = 10;  
    for (var i = 0, len = arrayAdd.length; i < len; i++) {  
    add += arrayAdd[i];  
  3. Filter unique values

    We can use Set to create a new array with only the unique values.
    const array = [4,5,4,6,32,5,3,5,7,1,3,4]
    const AnotherArray = [...new Set(array)];
    console.log(AnotherArray); // Result: [4, 5, 6, 32, 3, 7, 1]
  4. Comment your code often

    Comments are a great way to summarise a code fragment’s purpose, saving your time it would take to determine it on their own.
    // declaring and initialising variable x
    var x = 19
  5. Use strict mode to catch silent errors

    To opt into strict mode, add the line'use strict'; either at the top of your script section (if you want the whole section to be strict) or before the desired function (if only certain sections should be strict).
  6. Write shorter loops with array methods

    Instead of using
    const prices = ['4.0', '3.2', '2.45'];
    const formattedPrices = [];
    for (let i = 0; i < prices.length; i++) {
    const price = parseFloat(prices[i]);
    if (price) { formattedPrices.push(price) }
    It is better to use
    const prices = ['4.0', '3.2', '2.45'];;
    const formattedPrices = prices.map(price => parseFloat(price));
  7. Empty an array

    var someArray = ['apple' , 'banana' , 'watermelon' ];  
    someArray.length = 0; // someArray will be equal to [].
  8. Generate an array of numbers with numbers from 0 to max

    var someArray = [] , max = 50;
    for( var i=1; someArray.push(i++) < max;);
    console.log(someArray)   // someArray = [1,2,3 ... 50]
  9. use === instead of ==

    The == (or !=) operator performs an automatic type conversion if needed. The === (or !==) operator will not perform any conversion. It compares the value and the type, which could be considered faster than ==.
    [10] === 10    // is false
    [10]  == 10    // is true

    JavaScript is the only language that I'm aware of that people feel they don't need to learn before they start using it. ~Douglas Crockford

  10. Append an array to another array

    var firstArray = [13,5,3,6,2,'string',true];
    var secondArray = ["anotherstring" , 3,5,2,1 , false];
    Array.prototype.push.apply(firstArray, secondArray);
    // firstArray will be equal to [13, 5, 3, 6, 2, "string", true, "anotherstring", 3, 5, 2, 1, false]
  11. Don’t use delete to remove an item from array

    Use splice instead of using delete to delete an item from an array.Using delete replaces the item with undefined instead of the removing it from the array. Instead of Using
    var items = [13,5,3,6,2,'string',true];
    items.length; // return 7
    delete items[3]; // return true 
    items.length; // return 7
    console.log(items) // [13, 5, 3, empty, 2, "string", true]
    It is better to use
    var items = [13,5,3,6,2,'string',true];
    items.length; // return 7
    items.splice(3,1) ; 
    items.length; // return 6 
    console.log(items) // [13, 5, 3, 2, "string", true]
  12. Rounding number to N decimal place using toFixed

    var number =3.2198379128;
    number = num.toFixed(3); 
    console.log(number)  // num will be equal to 3.219
  13. Avoid using with() in your code

    When you use with(), it inserts a variable at the global scope. Thus, if another variable has the same name it could cause confusion and overwrite the value.
  14. Convert to String

    To quickly convert a number to a string, we can use the concatenation operator + followed by an empty set of quotation marks "" .
    const number = 21 + "";
    console.log(number); // Result: "21"
  15. Float to Integer

    If you want to convert a float to an integer, the faster way to truncate a float to an integer using |, the bitwise OR operator.
    console.log(33.9 | 0);  // 33
    console.log(-33.9 | 0); // -33
  16. Get the Last Item(s) in an Array

    The array method slice() can take negative integers, and if provided it will take values from the end of the array
    let someArray =  [13,5,3,6,2,'string',true];
    console.log(someArray.slice(-1)); // [true]
    console.log(someArray.slice(-4)); //  [6, 2, "string", true]
    console.log(someArray.slice(-5)); //  [3, 6, 2, "string", true]
  17. Avoid the use of eval()

    Useing of eval is expensive operations as each time it is called script engine must convert source code to executable code.
    var func2 = eval(functionCodeHere);
  18. Use switch/case statement instead of a series of if/else

    Using switch/case is faster when there are more than 3 cases, and it is more elegant. Avoid using it when you have more than 3 cases.
  19. Convert to Number

    let number = "21";
    number = +number;
    console.log(number); // 21
  20. Comma Operator

    In JavaScript, the , operator is used for evaluating each of its operands from left to right and returns the value of the last operand.
    let count = 10;
    let num = (count++, count);
    console.log(num); // 11
  21. Use a Minifier

    Before making your website live, It is better to use a JavaScript Minifier to minify your code, This will make your website load much faster


There are many other tips, tricks and best practices, so if you have any ones to add please share it in the comment section.

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