javascript find type of variable
> typeof "foo"
"string"
> typeof true
"boolean"
> typeof 42
"number"
if(typeof bar === 'number') {
//whatever
}javascript find type of variable
> typeof "foo"
"string"
> typeof true
"boolean"
> typeof 42
"number"
if(typeof bar === 'number') {
//whatever
}check data type in javascript
typeof("string"); //string
typeof(123); //numberhow to use typeof in javascript
//typeof() will return the type of value in its parameters.
//some examples of types: undefined, NaN, number, string, object, array
//example of a practical usage
if (typeof(value) !== "undefined") {//also, make sure that the type name is a string
//execute code
}how to use typeof in javascript
console.log(typeof 93);
// Output = "number"
console.log(typeof 'Maximum');
// Output = 'string'
console.log(typeof false);
// Output = "boolean"
console.log(typeof anUndeclaredVariable);
// Output = "undefined"typeof
// Numbers
typeof 37 === 'number';
typeof 3.14 === 'number';
typeof(42) === 'number';
typeof Math.LN2 === 'number';
typeof Infinity === 'number';
typeof NaN === 'number'; // Despite being "Not-A-Number"
typeof Number('1') === 'number'; // Number tries to parse things into numbers
typeof Number('shoe') === 'number'; // including values that cannot be type coerced to a number
typeof 42n === 'bigint';
// Strings
typeof '' === 'string';
typeof 'bla' === 'string';
typeof `template literal` === 'string';
typeof '1' === 'string'; // note that a number within a string is still typeof string
typeof (typeof 1) === 'string'; // typeof always returns a string
typeof String(1) === 'string'; // String converts anything into a string, safer than toString
// Booleans
typeof true === 'boolean';
typeof false === 'boolean';
typeof Boolean(1) === 'boolean'; // Boolean() will convert values based on if they're truthy or falsy
typeof !!(1) === 'boolean'; // two calls of the ! (logical NOT) operator are equivalent to Boolean()
// Symbols
typeof Symbol() === 'symbol'
typeof Symbol('foo') === 'symbol'
typeof Symbol.iterator === 'symbol'
// Undefined
typeof undefined === 'undefined';
typeof declaredButUndefinedVariable === 'undefined';
typeof undeclaredVariable === 'undefined';
// Objects
typeof {a: 1} === 'object';
// use Array.isArray or Object.prototype.toString.call
// to differentiate regular objects from arrays
typeof [1, 2, 4] === 'object';
typeof new Date() === 'object';
typeof /regex/ === 'object'; // See Regular expressions section for historical results
// The following are confusing, dangerous, and wasteful. Avoid them.
typeof new Boolean(true) === 'object';
typeof new Number(1) === 'object';
typeof new String('abc') === 'object';
// Functions
typeof function() {} === 'function';
typeof class C {} === 'function';
typeof Math.sin === 'function';how to use typeof in javascript
var someValue = 'this is string';
console.log(typeof(someValue)); // this will return stringCopyright © 2021 Codeinu
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