What control flow means in programming

Control flow means the order in which the program executes instructions. Normally, JavaScript runs code line by line from top to bottom. But sometimes we want the program to make decisions.

Example :

• If the user is loggedIn --> show dashboard

• Otherwise --> Signup page

Control flow statements helps us control the direction of execution.

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The if statement

The if statement is used to specify a block of code to be executed if a specified condition is true.

let a=10;

if(a>5){
    console.log('a is greater than 5');
}

Since a is greater than 5 so, the message a is greater than 5 will be printed to the console.

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The if-else statement

Sometimes , there will be time we want two possible outcomes. For example , a person is greater than 18 the person is eligible to vote or not eligible.

Syntax:

if (condition) {
  // code if true
} else {
  // code if false
}

Example :

let age = 16;

if (age >= 18) {
  console.log("You can vote");
} else {
  console.log("You cannot vote yet");
}

// output : You cannot vote yet

Since the condition does not satisfy so else block statements runs and print to the console.

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The else if statement

The else if statements comes into play when we have multiple conditions. For example, A grading system :

• 90+ --> Grade A

• 70+ --> Grade B

• 50+ --> Grade C

• Otherwise --> Fail

Syntax

if (condition1) {
   // code
} else if (condition2) {
   // code
} else if (condition3) {
   // code
} else {
   // default code
}

Example :

let marks = 75;

if (marks >= 90) {
  console.log("Grade A");
} else if (marks >= 70) {
  console.log("Grade B");
} else if (marks >= 50) {
  console.log("Grade C");
} else {
  console.log("Fail");
}

// output : Grade B

The program checks the condition from top to bottom and runs the first true condition. If the all the conditions are not met then it will runs the else block.

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The switch statement

The switch statement is another way to handle multiple conditions. It is often used when checking one variable against many possible values. It's a good alternative to a series of if.. else if statements when you have a single conditions that can lead to several possible outcomes.

Syntax

switch(expression) {
  case value1:
    // code to be executed if expression equals value1
    break;
  case value2:
    // code to be executed if expression equals value2
    break;
  ...
  default:
    // code to be executed if expression doesn't match any cases
}

Example

let day = "Monday";

switch (day) {
  case "Monday":
    console.log("Start of the week");
    break;

  case "Friday":
    console.log("Almost weekend");
    break;

  case "Sunday":
    console.log("Holiday");
    break;

  default:
    console.log("Regular day");
}

// output : Start of the week

The break statements stops the program from checking further cases.

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When to use switch vs if-else

Both can solve similar problems, but they are used in different conditions.

Use if-else when :

• You are checking ranges

• Conditions involve comparisons

Example :

if (score > 90)

Use switch when :

• You are checking one variable

• Comparing against specific values

Example :

switch(day)

Comparison if-else vs switch

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Wrapping Up 📌

Thanks for reading till the end 🙌
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