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Give examples of using the if…else statement for multiple conditions in JavaScript?
The if…else statement in JavaScript can be used to execute code based on multiple conditions. Here are some examples:
Checking if a number is between two values:
const num = 15;
if (num >= 10 && num <= 20) {
console.log("The number is between 10 and 20");
} else {
console.log("The number is not between 10 and 20");
}
Checking if a user is logged in and has admin privileges:
const isLoggedIn = true;
const isAdmin = false;
if (isLoggedIn && isAdmin) {
console.log("The user is logged in and has admin privileges");
} else if (isLoggedIn) {
console.log("The user is logged in but does not have admin privileges");
} else {
console.log("The user is not logged in");
}
Checking if a variable is a certain type:
const value = "Hello, world!";
if (typeof value === "string") {
console.log("The value is a string");
} else if (typeof value === "number") {
console.log("The value is a number");
} else {
console.log("The value is not a string or a number");
}
the if…else statement can be used to execute code based on multiple conditions. It is a very powerful tool for writing conditional logic in JavaScript.
Here are some rules to follow when using the if…else statement for multiple conditions:
The
conditionmust be a Boolean expression.The
ifblock and theelseblock must be terminated by a semicolon.The
ifblock and theelseblock can contain any valid JavaScript code.The
elseblock is optional, but it is a good practice to include it in case theconditionevaluates to false.
How do use the conditional operator in a one-liner if…else statement in JavaScript?
The conditional operator in JavaScript is a ternary operator that can be used to write one-liner if…else statements. The syntax of the conditional operator is:
condition ? value_if_true : value_if_false;
The condition is a Boolean expression that evaluates to either true or false. If the condition evaluates to true, the value of the value_if_true expression is returned. If the condition evaluates to false, the value of the value_if_false expression is returned.
Here is an example of a one-liner if…else statement using the conditional operator:
const num = 10;
const message = num > 5 ? "greater than 5" : "less than or equal to 5";
console.log(message); // "greater than 5"
This code first checks if the value of the variable num is greater than 5. If the value of num is greater than 5, the value of the value_if_true expression, which is “greater than 5”, is returned. If the value of num is not greater than 5, the value of the value_if_false expression, which is “less than or equal to 5”, is returned.
The conditional operator can be used to write one-liner if…else statements in any way you want. It is a very powerful tool for writing concise and efficient code.
Here are some other examples of using the conditional operator in a one-liner if…else statement:
// Check if a number is between 10 and 20
const num = 15;
const message = num >= 10 && num <= 20 ? "between 10 and 20" : "not between 10 and 20";
// Check if a user is logged in and has admin privileges
const isLoggedIn = true;
const isAdmin = false;
const message = isLoggedIn && isAdmin ? "logged in and has admin privileges" : isLoggedIn ? "logged in" : "not logged in";
The conditional operator can be a very useful tool for writing concise and efficient code. It is a good practice to use it whenever possible.
What is the use of the else if statement in JavaScript?
The else if statement in JavaScript is used to execute code based on multiple conditions. It is a conditional statement that is similar to the if…else statement, but it allows you to check multiple conditions and execute different code depending on the outcome of each condition.
The syntax of the else if statement is:
if (condition) {
// code to be executed if condition is true
} else if (condition) {
// code to be executed if condition is true
} else {
// code to be executed if neither condition is true
}
The condition is a Boolean expression that evaluates to either true or false. If the condition evaluates to true, the code inside the if block is executed. If the condition evaluates to false, the code inside the else if block is executed. If neither of the if or else if conditions evaluates to true, the code inside the else block is executed.
Here is an example of an else if statement:
const num = 10;
if (num > 5) {
console.log("The number is greater than 5");
} else if (num === 5) {
console.log("The number is equal to 5");
} else {
console.log("The number is less than or equal to 5");
}
This code first checks if the value of the variable num is greater than 5. If the value of num is greater than 5, the code inside the if block is executed. If the value of num is not greater than 5, the code inside the else if block is executed. If the value of num is not equal to 5, the code inside the else block is executed.
The else if statement can be used to execute code based on multiple conditions. It is a very powerful tool for writing conditional logic in JavaScript.
Here are some rules to follow when using the else if statement:
The
conditionmust be a Boolean expression.The
ifblock,else ifblocks, andelseblock must be terminated by a semicolon.The
ifblock,else ifblocks, andelseblock can contain any valid JavaScript code.The
elseblock is optional, but it is a good practice to include it in case none of theiforelse ifconditions evaluate to true.
Provide examples of using the switch statement for multiple cases in JavaScript?
The switch statement in JavaScript is a conditional statement that is used to execute code based on the value of a variable or expression. The switch statement has the following syntax:
switch (expression) {
case value1:
// code to be executed if expression is equal to value1
break;
case value2:
// code to be executed if expression is equal to value2
break;
default:
// code to be executed if expression is not equal to any of the values
}
The expression is a variable or expression that is evaluated. The value of the expression is then compared to the values in the case statements. If the value of the expression is equal to the value of a case statement, the code inside the case statement is executed. The break statement is used to exit the switch statement. If the value of the expression is not equal to any of the values in the case statements, the code inside the default block is executed.
Here is an example of a switch statement:
const color = "red";
switch (color) {
case "red":
console.log("The color is red");
break;
case "green":
console.log("The color is green");
break;
case "blue":
console.log("The color is blue");
break;
default:
console.log("The color is not red, green, or blue");
}
This code first checks the value of the variable color. If the value of color is equal to “red”, the code inside the case "red" block is executed. If the value of color is equal to “green”, the code inside the case "green" block is executed. If the value of color is equal to “blue”, the code inside the case "blue" block is executed. If the value of color is not equal to any of the values in the case statements, the code inside the default block is executed.
The switch statement can be used to execute code based on the value of a variable or expression. It is a very powerful tool for writing conditional logic in JavaScript.
Here are some rules to follow when using the switch statement:
The
expressionmust be a variable or expression that can be evaluated to a value.The
casestatements must be terminated by a semicolon.The
breakstatement is optional, but it is a good practice to use it to exit the switch statement.The
defaultblock is optional, but it is a good practice to include it in case the value of the expression does not match any of thecasestatements.
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