Flow control using JS

Yes, it's one of the most important topic when you are learning how to write code with JS 🤔

First, you need to understand what does it mean, what is exactly flow control, when your code needs to take a decision about which sentence should be run it's made with FLOW CONTROL 😇. There are different methods to control flow using JS, let's going to see some examples:

if - else clause

This is the most typical one, it gives us a lot of control about code execution, we can decide which code should be run

if (condition) {
 // run here is condition is true
} else {
 // run here is condition is false
}

This is the basic syntax you must use 😁, it's really easy, you have a condition which is evaluated and depending on that you will run one side or another. OMG!! Yes, it gives us a lot of power. Let's try one more example:

const myMum = "Maria";
if (typeof myMum === 'string') {
 console.log("My mum contains a string");
} else {
 console.log("My mum is not a string");
}

As you have just seen, this code checks if this const is a string and run the following sentences according to the condition, obviously this condition is true, the you will see My Mum contains a string in your console 😇.

Moreover you are able to evaluate multiple conditions using logic operators, AND && and OR ||.

• AND &&: It means that all the conditions must be true due to true of the entire condition.

// It returns true due to both sides are true.
true===true

• OR ||: It means that at least one of the conditions must be true to get a final true:

// it returns true due to at least one side is true
true || false

It gives us more powerful tools to check multiple conditions using the same if clause 🤖

const myMum = "Maria";
if (true && typeof myMum === 'string') {
 console.log("My mum contains a string");
} else {
 console.log("My mum is not a string");
}

As you have just seen, it will print My mum contains a string because two conditions are true and I have used an AND logic port.
I recommend you to practise some conditions using JS to understand better ☺️ how to use that.

Switch-case clause

It allows you to check multiple static conditions and take decisions depending on that value.

switch (condition) {
  case valor1:
    // It will run when the conditions is match `valor1` 
    [break;]
  case valor2:
    // It will run when the conditions is match `valor2` 
    [break;]
  ...
  case valorN:
    // It will run when the conditions is match `valorN` 
    [break;]
  default:
    // It will run when all the conditions are false
    [break;]
}

It has a lot of power and bring us the opportunity to check multiple possible values easily, instead, we can use multiple if-else clauses, but your code will not be legible 🤒. It comes to bring us more organisation when we need to check conditions that can take a lot different values, Let's see an example:

const foo = 0;
switch (foo) {
  case -1:
    console.log('1 negative');
    break;
  case 0: // foo is 0, then the following block will be run
    console.log(0)
  break; // Break allow us not to run case1
  case 1: 
    console.log(1);
    break; // Break allow us not to run case2
  case 2:
    console.log(2);
    break;
  default:
    console.log('default');
}

Moreover, you can run the same for conditions that need to perform the same action, let's see an example:

const animal = 'giraffe';
switch (Animal) {
  case 'Dog':
  case 'giraffe':
  case 'Cat':
  case 'Bird':
    console.log('This animal will live.');
    break;
  case 'elephant':
  default:
    console.log('This animal will not.');
}

As you have just seen, we will take the same action if animal math one of the four case exposed 😇.

Here you have seen how to check conditions and how to make your code take decisions in execution time about possible values of your expressions.

That's all for today post!!!

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