if conditional statement

The if conditional statement allows us to check if a given condition is fulfilled. We commonly use logical operators in conditional statements.

let x = parseInt(prompt("Enter a number:"))
if (x === 5)
    console.log("The user entered the number 5.")
                                    

We use the modulo operator very often in conditional statements. In the example below, the condition checks if the x variable is divisible by 2 (whether it is even).

let x = parseInt(prompt("Enter a number:"))
if (x % 2 === 0)
    console.log("The user entered an even number.")
                                    

We can simplify the if statement by using boolean conditions. We can just write if(x), and if x is true, the instruction will be executed. true means any value other than 0.

else and else if conditional statements

else is a statement that allows us to simplify our code by avoiding the need for another if statement, replacing it with an alternative action when the original condition is false.

let x = parseInt(prompt("Enter a number:"))
if (x > 0)
    console.log("The user entered a positive number.")
else
    console.log("The user entered a negative number.")
                                    

The code above doesn't handle the case where the user enters 0. To do that, we need else if. It works similarly to else, but allows us to specify an additional condition (like in an if statement). We can use as many else if instructions as we want, relating to a single if.

let x = parseInt(prompt("Enter a number:"))
if (x > 0)
    console.log("The user entered a positive number.")
else if (x < 0)
    console.log("The user entered a negative number.")
else
    console.log("The user entered 0.")
                                    

We use this instruction instead of writing multiple if statements because if any of the conditions relating to a single if statement have been met, the rest will not be considered.

break and continue keywords

The break keyword is used to break the continuity of a loop, and continue can skip particular iterations within it.

let x
while (true) {
    x = parseInt(prompt("Enter a number:"))
    if (x > 0)
        break
}

for (let y = 1; y <= 10; y++) {
    if (y === 4 || y === 8) 
        continue
    console.log(y)
}
                                    

switch conditional statement

switch is an instruction that simplifies complex conditions by replacing multiple if and else if statements with a more concise structure.

let x = parseInt(prompt("Enter a number:"))

switch(x) {
    case 0:
        console.log("x equals 0")
        break
    case 25:
        console.log("x equals 25")
        break
    case 50:
        console.log("x equals 50")
        break
    default:
        console.log("x doesn't equal 0, 25, or 50")
}
                                    

A parameter of the switch statement is usually an integer or a string (but it could be something else).

If we want several cases to be called upon in a given case, we do not put the break statement at the end of it (they will execute until a break is encountered or the switch instruction ends).

The ternary operator (?)

The ternary operator allows us to create a simplifed one-line version of the if-else statement. If the condition is true, the instruction on the left side of the colon will execute, and if not - the one on the right side. Check the results in your editor.

console.log(7 > 4 ? 4 : 7)

let a = 7, b = 10
let x = a >= b ? "a >= b" : "a <= b"

console.log(x)