Control Flow
If Statement in JavaScript
The if else block controls decision making by checking true/false statements resulting in different executions of code, depending on if the result is true and if the result is false.
There are three parts to the if-else block: if, else if, and else.
Syntax
if(booleanExpression) {
//Executes when booleanExpression holds true
}
else if(booleanExpression2) {
//Executes when booleanExpression2 holds true
}
else {
//Executes when neither booleanExpression nor booleanExpression2 are true
}Notes
booleanExpression(s) are those that result in either a true or false output. They are created using comparing operators (==, >, =, <=, !=).
There can also be multiple Boolean expressions within the parentheses (booleanExpression). The Boolean expressions are connected through logical operators (&&, ||, !).
Else if statements allow for another Boolean expression check within the overall if structure. This is optional.
Else statements result in the execution of code if the if statement (and if applicable, the subsequent else if statement(s)) do not hold true.
Nested if (else) statements are also possible and are the inclusion of another (or multiple) if statements within an if statement block.
Example
if(counter >= 30) {
console.log("Counter is greater than 30.");
}
else if (counter ==20) {
console.log("Counter is at 20.");
counter++;
}
else {
counter++;
}