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JavaScript - convert string to boolean

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Created by:

a_horse

538

In this article, we would like to show you how to parse a string to a boolean in JavaScript

Quick solution:

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var text = 'true';
​
console.log(text === 'true');  // true

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JSON parse example

Edit

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function parseBoolean(text) {
    var value = JSON.parse(text);
    if(typeof value !== 'boolean') {
        throw new Error('Incorrect type!');
    }
    return value;
}
​
​
// Usage example:
​
var text = 'true';
var value = parseBoolean(text);
​
console.log(value);  // true

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Regular expression example

Edit

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var truthExpression = /^(TRUE|True|true|YES|Yes|yes|ON|On|on|1|T|t|Y|y)$/g;
var falsyExpression = /^(FALSE|False|false|NO|No|no|OFF|Off|off|0|F|f|N|n)$/g;
​
function parseBoolean(text) {
    if (truthExpression.test(text)) {
        return true;
    }
    if (falsyExpression.test(text)) {
        return false;
    }
    throw new Error('Incorrect value!');
}
​
​
// Usage example:
​
var text = 'true';
var value = parseBoolean(text);
​
console.log(value);  // true

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Custom function example

Edit

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function parseBoolean(value) {
    switch(value) {
        case 1:
        case true:
        case "1":
        case "true":
        case "True":
        case "TRUE":
        case "on":
        case "On":
        case "ON":
        case "yes":
        case "Yes":
        case "YES":
        case "t":
        case "T":
        case "y":
        case "Y":
            return true;
        case 0:
        case false:
        case "0":
        case "false":
        case "False":
        case "FALSE":
        case "off":
        case "Off":
        case "OFF":
        case "no":
        case "No":
        case "NO":
        case "f":
        case "F":
        case "n":
        case "N":
            return false;
        default:
            throw new Error('Incorrect value!');
    }
}
​
​
// Usage example:
​
var text = 'true';
var value = parseBoolean(text);
​
console.log(value);  // true