Conditional Statements:
- In JavaScript, conditional statements control the program flow by executing specific blocks of code based on whether a condition evaluates to true or false.
- They are essential for decision-making in scripts, enabling dynamic and interactive behavior.
- Conditions are evaluated using comparison and logical operators.
- They help in building dynamic and interactive applications by responding to different inputs.
Types of Conditional Statements:
1. if Statement:
- The if statement checks a condition written inside parentheses.
- If the condition evaluates to true, the code inside {} is executed; otherwise, it is skipped.
- Executes code only when a specified condition is true.
- Useful for making simple decisions in a program.
syntax:
if (condition) {
// block of code to be executed if the condition is true
}
example:
let mark = 35;
if(mark>=35){
console.log("pass")
}
output:
pass
2. if...else Statement:
- The if-else statement executes one block of code if a condition is true and another block if it is false.
- It ensures that exactly one of the two code blocks runs.
- Used when there are two possible outcomes.
- The else block runs when the if condition is not satisfied.
syntax:
if (condition) {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}
example:
let age = 17;
if(age>=18){
console.log("eligible to vote")
}else{
console.log("not eligible to vote")
}
output:
not eligible to vote
3. if...else if...else Ladder:
- The else if statement is used to test multiple conditions in sequence.
- It executes the first block whose condition evaluates to true.
- Allows checking more than two conditions.
- Evaluated from top to bottom until a true condition is found.
syntax:
if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if the condition1 is false and condition2 is true
} else {
// block of code to be executed if the condition1 is false and condition2 is false
}
example:
let score = 75;
if (score >= 90) {
console.log("Grade: A");
} else if (score >= 75) {
console.log("Grade: B");
} else if (score >= 50) {
console.log("Grade: C");
} else {
console.log("Grade: F");
}
output:
Grade: B
4. switch Statement:
- The switch statement evaluates an expression and executes the matching case block based on its value.
- It provides a clean and readable way to handle multiple conditions for a single variable.
- Used when one variable needs to be compared against multiple fixed values.
- Improves readability compared to long if...else if chains.
syntax:
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}
example:
let day = 3;
switch (day) {
case 1:
console.log("Monday");
break;
case 2:
console.log("Tuesday");
break;
case 3:
console.log("Wednesday");
break;
case 4:
console.log("Thursday");
break;
case 5:
console.log("Friday");
break;
case 6:
console.log("Saturday");
break;
case 7:
console.log("Sunday");
break;
default:
console.log("Invalid day");
}
output:
Wednesday
5. Ternary Operator (? :):
- The ternary operator is a compact shorthand for an if...else statement.
- It is called “ternary” because it takes three operands:
- A condition to test.
- An expression to evaluate if the condition is true.
- An expression to evaluate if the condition is false.
syntax:
(condition) ? expression1 : expression2
example:
let age = 18;
let message = (age >= 18) ? "Eligible to vote" : "Not eligible";
console.log(message);
output:
Eligible to vote
6. Nested if...else:
- A nested if...else statement is an if...else block written inside another if or else.
- It is used to evaluate multiple related conditions in a hierarchical manner.
- Useful for handling complex decision-making logic.
- Deep nesting should be avoided to maintain code readability.
example:
let tam = 37;
let eng = 45;
let mat = 67;
let sci = 56;
let soc = 77;
let total;
let avg;
if (tam>=35 && eng>=35 && mat>=35 && sci>=35 && soc>=35){
console.log("pass")
total = (tam + eng + mat + sci + soc);
console.log(total)
avg = total/5;
console.log(avg)
if (avg>=70){
console.log("grade a");
}else if(avg>=50){
console.log("grade b")
}else{
console.log("grade c")
}
}else{
console.log("fail");
}
output:
pass
282
56.4
grade b
References:
JavaScript - Conditional Statements - GeeksforGeeks
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