If Statements (Conditionals)

What is an `if` statement?

An if statement allows you to run some code ONLY if the condition provided is true.

var someCondition = true;

if (someCondition) {
  // instructions in this block will run when SOME_CONDITION evaluates to "true"
}

if (true) {
  // not very useful, since this will ALWAYS be true
} 

Comparison operators

When evaluating the truth of a condition, it’s often helpful to compare to values. That’s where we use comparison operators.

// <  >  <= >= == ===
if (3>5) {} // greater than
if (3<5) {} // less than

if (3>=5) {} // greater than OR equal to 
if (3<=5) {} // less than OR equal to

if (3=='3') {} // equality. Returns true
// -> true
if (3==='3') {} // strict equality. Includes type comparison.
// -> false

if (3!='3') {} // non-equality. Like opposite of `==`. If 3 is NOT equal '3'
// -> false 
if (3!=='3') {} // non-strict equality. If 3 is NOT equal AND NOT same type as '3'
// -> true 

=== is usually recommended over ==.

`else` and `else if`

Sometimes you want to check for multiple conditions when only 1 should be the case.

// these conditions will be checked in order. When a condition is true, 
// ONLY that block will run.
if (a>b) { 
  // do something if a is greater than b
} else if (a<b) {
  // do something else if a is less than b
} else {
  // do something else if neither of the above conditions are true
}
 

AND and OR

Want to combine 2 or more conditions? Use the && AND operator, or the || OR operator.

if (a>5 && a<10) {} // is "a" greater than 5 AND less than 10?
if (a>5 || a>10) {} // is "a" greater than 5 OR is "a" greater than 10? 

Exercises. Now you try it.

// 1. Add an additional check (try to use "else if") for "less than 5" and modify the result message
//    when that happens
// 2. Add an "else" block for the condition that it is exactly 5 and modify the
//    result message.
// 3. Test your logic by changing the input number.
var result;
var input = 7;

if (input > 5) {
  result = "Input is bigger than 5!";
}

result
 