Currying simply means evaluating functions with multiple arguments and decomposing them into a sequence of functions with a single argument.
Currying is an advanced technique to transform a function of arguments n, to n functions of one or less arguments.
In Javascript, functions can be assigned to variables in the same way that strings or arrays can. They can be passed into other functions as parameters or returned from them as well. A “higher-order function” is a function that accepts functions as parameters and/or returns a function.
Functions that operate on other functions, either by taking them as arguments or by returning them, are called higher-order functions.
Higher order functions are a result of functions being first-class citizens in javascript.
Immediately-Invoked Function Expressions (IIFE), pronounced “iffy”, are a common JavaScript pattern that executes a function instantly after it’s defined. Developers primarily use this pattern to ensure variables are only accessible within the scope of the defined function.
A statically-typed language is a language (such as Java, C, or C++) where variable types are known at compile time. In most of these languages, types must be expressly indicated by the programmer; in other cases (such as OCaml), type inference allows the programmer to not indicate their variable types
A language is dynamically-typed if the type of a variable is checked during run-time. Common examples of dynamically-typed languages includes JavaScript, Objective-C, PHP, Python, Ruby, Lisp, and Tcl.
avaScript is a dynamically typed language. In a dynamically typed language, the type of a variable is checked during run-time in contrast to statically typed language, where the type of a variable is checked during compile-time.
NaN property represents “Not-a-Number” value. It indicates a value which is not a legal number.
typeof of a NaN will return a Number .
To check if a value is NaN, we use the isNaN() function
Implicit type coercion in javascript is automatic conversion of value from one data type to another. It takes place when the operands of an expression are of different data types.
String coercion
String coercion takes place while using the ‘ + ‘ operator. When a number is added to a string, the number type is always converted to the string type.
When JavaScript sees that the operands of the expression x + y are of different types ( one being a number type and the other being a string type ) , it converts the number type to the string type and then performs the operation. Since after conversion, both the variables are of string type, the ‘ + ‘ operator outputs the concatenated string “33” in the first example and “24Hello” in the second example.
All these 4 jQuery methods are used for attaching events to selectors or elements. But they all are different from each other.
.bind(): This is the easiest and quick method to bind events. But the issue with bind() is that it doesn’t work for elements added dynamically that matches the same selector. bind() only attach events to the current elements not future element. Above that it also has performance issues when dealing with a large selection.
.live(): This method overcomes the disadvantage of bind(). It works for dynamically added elements or future elements. Because of its poor performance on large pages, this method is deprecated as of jQuery 1.7 and you should stop using it. Chaining is not properly supported using this method.
.delegate(): The .delegate() method behaves in a similar fashion to the .live() method, but instead of attaching the selector/event information to the document, you can choose where it is anchored and it also supports chaining.
.on(): Since live was deprecated with 1.7, so new method was introduced named “.on()”. This method provides all the goodness of previous 3 methods and it brings uniformity for attaching event handlers.
All these methods .empty(), .remove() and .detach() are used for removing elements from DOM but they all are different.
.empty(): This method removes all the child element of the matched element where remove() method removes set of matched elements from DOM.
.remove(): Use .remove() when you want to remove the element itself, as well as everything inside it. In addition to the elements themselves, all bound events and jQuery data associated with the elements are removed.
.detach(): This method is the same as .remove(), except that .detach() keeps all jQuery data associated with the removed elements. This method is useful when removed elements are to be reinserted into the DOM at a later time.
document.ready() function is different from body onload() function for 2 reasons.