javascript typeof shows object
What value it has What the output shows you
when you write |console.log(typeof(variable);
Undefined: "undefined"
Null: "object"
Boolean: "boolean"
Number: "number"
String: "string"
Function object: "function"
E4X XML object: "xml"
E4X XMLList object: "xml"
NodeList "Nodelist [more data]"
HTMLCollection "HTMLCollection(1) [more data]"type of variable js
// get type of variable
var number = 1
var string = 'hello world'
var dict = {a: 1, b: 2, c: 3}
console.log(typeof number) // number
console.log(typeof string) // string
console.log(typeof dict) // objectisPrototypeOf js
/"Checks if an object exists in another object's prototype chain."/
function Bird(name) {
this.name = name;
}
let duck = new Bird("Donald");
Bird.prototype.isPrototypeOf(duck);
// returns truecheck type javascript
console.log(typeof "how are you?")
"string"
console.log(typeof false) / console.log(typeof true)
"boolean"
console.log(typeof 100)
"number"javascript find type of variable
> typeof "foo"
"string"
> typeof true
"boolean"
> typeof 42
"number"
if(typeof bar === 'number') {
//whatever
}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';Copyright © 2021 Codeinu
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