DEV Community: Syed Faysel Ahammad Rajo

All types of loop in JavaScript

Syed Faysel Ahammad Rajo — Sun, 14 May 2023 19:27:48 +0000

For Loop

While loop

Do while loop

Apart from this three traditional loop, there two shortcut loop in newer javaScript.

Useful shortcut loop (for of, for in)

For of loop

To loop over an array we can use the for of loop.

let nums = [2,3,4,5,6,7];
for (const num of nums){
   console.log(num);
}

For in loop

To loop over an object, we can use for in loop

let info = {
    name : "rajo",
    id : 124,
    isAlve : true
};
for (const key in info){
   console.log(info[key]);
}

JavaScript Filter() method

Syed Faysel Ahammad Rajo — Wed, 10 May 2023 15:07:20 +0000

JavaScript filer method creates a new array with all elements that pass the test or condition implemented by the provided function. Following example will make it more clear.

const nums = [1,2,3,4,5,6,7,8,9,10];
const even = nums.filter(n => n % 2 == 0);
//this will return an array with all even numbers

Here in the filter method, we used an arrow function as arguments. What filter method does is, loop over the array or object and pass element through the provided function. If the condition is true then the output is added to the new array.

JavaScript arrow function

Syed Faysel Ahammad Rajo — Wed, 10 May 2023 13:37:36 +0000

JavaScript Function:

function greet(){
    console.log("Hello world");
}

JavaScript regular function expression:

A regular function expression is like storing something into a variable. Following example might help you understand it better. We declare a variable,and then we write down the function.

const greet =  function(){
    console.log("Hello world");
}

Arrow function

Now, here comes the arrow function. Arrow function is nothing but syntactically a compact alternative to a regular function expression.

const greet = () => {
    console.log("Hello world");
}

Notice there is no function keyword in the above function expression. instead we just use an arrow and the curly braces. Also, we use parentheses before the => sign, where we can pass any arguments/parameters if needed.

const greet = (name) => {
    console.log(`Hey ${name}!`);
}

We can do a lot more using arrow function. Here is a short trick if we want to return something.

const add = (x,y) => {
    return x+y;
}

Instead of writing the return keyword and using curly braces, we put the statement or expression which need to be returned inside a parentheses and that's it.

const add = (x,y) => (
    x+y;
)

We can write even more shorter if we use single line statement.

const add = (x, y) => x + y;

In that case we don't even need to use any parentheses or curly braces.

Summary

const greet =  function(){ //regular function expression
    console.log("Hello world");
}

const greet = (name) => { //arrow function with parens around param
    console.log(`Hey ${name}!`);
}

const greet = name => { //no parens around param
    return (`Hey ${name}!`);
}
const greet = name => ( //implicit return
    `Hey ${name}!`;
)

const isEven = num => num % 2 === 0 //one liner implicit return

Thanks for reading.
Read my other articles : Dev blogs

List Comprehension in Python

Syed Faysel Ahammad Rajo — Wed, 14 Sep 2022 22:28:07 +0000

What is List Comprehension?

List comprehension is nothing just a shorter way to create a list from another list or iterable instead of using an actual loop or something else. Hence, it list comprehension makes the code or syntax shorter and clean.

The code below is a very basic example of list comprehension.

Creating a list from another list using loop

nums = [1,2,3,4,5]
newList = []
for i in nums:
    newList.append(i)

Now observe the code below which uses list comprehension

Creating a list from another list using list comprehension

nums = [1,2,3,4,5]
newList = [i for i in nums]

That's it. See, how shorter the code is. Now, let's explain what happened here. The first 'i' inside the newList is the item to be append, and the next part for i in nums is simply nothing but a loop. This portion of code iterates over the list nums. Then each item is added to the newList.

Even we can make list comprehension more complex. We can use expression, condition in this comprehension.

Like the following example. Let's say we want a list containing the elements which are the squared of even elements from another list.

Hence the code looks like this:

nums = [1,2,3,4,5]
newList = [i**i for i in nums if i%2==0]

See, How simple! List comprehension comes handy. It saves much time & keeps the code clean. Python programmer should utilize the benefits of list comprehension.

Thanks for reading. Hope this article makes you understood list comprehension.
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