04_JS_Conditionals

Software-Engineering

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# Why using Conditionals?

To make decisions based on different conditions. Executed: from top ⇾ bottom

There are two ways an execution can be altered:

1. conditional execution: statements are executed if a expression is true.
2. repetive execution: statements are repetitively executed as long as expression is true.

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# Implementation

if
if else
if else if else
switch
ternary operator

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# Examples

# If Statement

let num = 3
if (num > 0) {
  console.log(`${num} is a positive number`)
}
//  3 is a positive number

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# If-else Statement

let num = -3
if (num > 0) {
  console.log(`${num} is a positive number`)
} else {
  console.log(`${num} is a negative number`)
}
//  -3 is a negative number

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# If else-if else Statement

let a = 0
if (a > 0) {
  console.log(`${a} is a positive number`)
} else if (a < 0) {
  console.log(`${a} is a negative number`)
} else if (a == 0) {
  console.log(`${a} is zero`)
} else {
  console.log(`${a} is not a number`)
}

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# Switch Statement

let weather = 'cloudy'
switch (weather) {
  case 'rainy':
    console.log('You need a rain coat.')
    break
  case 'cloudy':
    console.log('It might be cold, you need a jacket.')
    break
  case 'sunny':
    console.log('Go out freely.')
    break
  default:
    console.log(' No need for rain coat.')
}

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# Ternary operator

Here we replace if(true) { … } else …

let isRaining = true
isRaining
  ? console.log('You need a rain coat.')
  : console.log('No need for a rain coat.')

Here the variable name is “Pedro”, when the age is greater than 10

let age = 10;
let name = age > 10 && "Pedro"
// This would be the opposite
let name = age > 10 || "Pedro"

let age = 16;
let name = age > 10 ? "Pedro" : "Jack";

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