JavaScript - Convert a String to Boolean in JS

Here are different ways to convert string to boolean in JavaScript.

1. Using JavaScript == Operator

The == operator compares the equality of two operands. If equal then the condition is true otherwise false. 

Syntax

console.log(YOUR_STRING == 'true');

let str1 = "false";
console.log(str1 == 'true');

let str2 = "True";
console.log(str2.toLowerCase() == 'true');

false
true

2. Using JavaScript === Operator

This operator compares the equality of two operands with type. If equal(type and value both) then the condition is true otherwise false. It strictly checks the condition.

Note: As the operator strictly checks the condition, so if you do not use toLowerCase(), then it will give you the "false" as a Boolean value.

let str = "true";
console.log(str === 'true');

str = "True";
console.log(str.toLowerCase() === 'true');

true
true

3. Using Boolean() Function

The boolean function returns the boolean value of the variable. It can also be used to find the boolean result of a condition, expression, etc. The Boolean() function evaluates the input and returns a boolean value. In this case, since the input string "true" is non-empty, the Boolean() function returns true.

let str = "true";
let result = Boolean(str);
console.log(result); 

true

4. Using a Regular Expression

We can use regular expression to convert a string to a Boolean value in JavaScript.

The regular expression /^true$/i is used with the test() method to check if the string matches the pattern "true" (case-insensitive). The ^ symbol denotes the start of the string, $ denotes the end of the string, and the i flag makes the pattern case-insensitive.

let str = "true";
let boolValue = /^true$/i.test(str);
console.log(boolValue); 

true

5. Using !! (Double Negation) Operator

The !! (double negation) operator is a commonly used approach to convert a string to a boolean value in JavaScript. The first negation (!) converts the string into its opposite boolean value, and the second negation (!) reverts it back to the original boolean value. that helps us to change the given string to boolean value.

let str = "true";
let boolValue = !!str;
console.log(boolValue); 

true

6. Using JSON.parse() Method

The JSON.parse() method can be used to convert a string to a boolean value in JavaScript. JSON.parse() method is used to parse the string "true" and convert it into its corresponding boolean value, which is true.

let str = "true";
let boolValue = JSON.parse(str);
console.log(boolValue); 

true

7. Using Ternary Operator

The ternary operator can also be used to convert a string to a boolean, the code employs a concise one-liner. The toLowerCase() method is applied to ensure case-insensitive comparison. The ternary operator checks if the lowercase string is equal to 'true'. If the condition is met, it returns true; otherwise, it returns false.

function stringToBooleanTernary(str) {

    // Ternary operator: condition ? true-value : false-value
    return str.toLowerCase() === 'true' ? true : false;
}

// Example usage
const resultTernary = stringToBooleanTernary('True');
console.log(resultTernary); // Output: true

true

8. Using Switch Case

The switch case approach involves using a switch statement to evaluate the lowercase string. Cases are defined for 'true' and 'false', each returning the corresponding boolean value. The default case is included to handle invalid input by throwing an error.

function stringToBooleanSwitch(str) {
    switch (str.toLowerCase()) {
        case 'true':
            return true;
        case 'false':
            return false;
        default:
            throw new Error('Invalid boolean string');
    }
}

// Driver code
try {
    const resultSwitch = stringToBooleanSwitch('False');
    console.log(resultSwitch); // Output: false
} catch (error) {
    console.error(error.message);
}

false