The syntax of typeof operator is: typeof operand typeof (operand). The typeof operator is a unary operator that returns a string representing the type of a variable. The typeof operator returns a string indicating the type of the unevaluated operand. 54 Answers Sorted by: 1 2 Next 2362 If typeof yourVariable object, its an object or null. alert (typeof undefinedVariable) // alerts the string 'undefined' alert (undefinedVariable instanceof Object) // throws an exception A good reason to use instanceof is if the variable may be null. In JavaScript, any value has a type assigned. typeof typeof typeof A js data type 'number', 'string', 'boolean', 'object', 'function', 'undefined', 'symbol', 'bigint' // Number. A good reason to use typeof is if the variable may be undefined. There’s hardly ever a reason for using = over = – if you’re comparing to true or false and you want coercion (for example you want 0 or '' to evaluate to false) then just use if(! empty_str) rather than if(empty_str = false).Learn the basics of the JavaScript typeof Operator The thinking is that you can either think about whether to use = or = every time you check for equality, or you can just get into the habit of always writing =. Arrays use numbers to access its 'elements'. But, JavaScript arrays are best described as arrays.
The recommendation from Crockford is that it’s safer to use = in many circumstances, and that if you’re going to use it in some circumstances it’s better to be consistent and use it for everything. The typeof operator in JavaScript returns 'object' for arrays. Use typeof to solve some basic problem (String, Number, Boolean.) and use to solve something complex (like Array, Date, RegExp). Try it Syntax object instanceof constructor Parameters object The object to test. the is a good way, but its performance is the worst. Its behavior can be customized with Symbol.hasInstance. Below is the reason why you may want to use = anyway. instanceof - JavaScript MDN instanceof The instanceof operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. To answer the main question – there is no danger in using typeof with =. There is no JavaScript primitive for functions, functions are objects that inherit from the global Function class.
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