Javascript Calling a Function Onload and Then Again

Developers use JavaScript call function to apply the same function to more than than 1 object. In other words, you can make a method or a function, already assigned to a specific object, be invoked for some other object also.

In this tutorial, you will learn nigh JavaScript phone call office options. You will understand how to call a function in JavaScript as a function and as a method. Nosotros will also explain JavaScript call function options, such as function constructor and part method. Moreover, you will become acquainted with the this keyword.

Contents

• 1. JavaScript Call Function: Main Tips
• 2. Using this Keyword
• 3. Invoking a Function
• three.ane. As a Function
• 3.2. As a Method
• 3.3. Using a Part Constructor
• three.four. Using a Function Method
• 4. JavaScript Call Function: Summary

JavaScript Call Part: Main Tips

• Function invocation is more oftentimes named simply calling a function.
• A block of code in a function is executed when the function is invoked.
• There are a few JavaScript phone call function options.
• this keyword in JavaScript represents an object containing electric current lawmaking.

Using this Keyword

When a office does not take an owner object, the global object becomes the value of this keyword. The global object in a webpage is the browser window.

In the example beneath, the value of this keyword is the window object:

Example

                                                function                  simpleFunction()                {                return                this;   }    simpleFunction();            

Invoking a Role

So, how to telephone call a office in JavaScript? The call part can be invoked as either a function or a method. What is more, it tin can be performed past using function methods and constructors.

Nosotros will now review all options one by i, and so you could understand the differences and cases in which they should exist used. As usual, lawmaking examples will be used to illustrate the concepts better.

Every bit a Function

The case below displays a function that does not belong to any object. Really, by default, it belongs to a global object window. Yous tin use it with the window prefix (window.simpleFunction()) but it is not necessary.

Instance

                                                function                  simpleFunction(x, y)                {                return                x * y;   }  simpleFunction(ten,                6);                // will return 60                          

Note: This instance executes a global function. While information technology is a common way to invoke a function in JavaScript, it is non considered as good practice in computer programming. Global variables can conflict with local ones and create bugs.

Pros

• Simplistic design (no unnecessary information)
• High-quality courses (fifty-fifty the free ones)
• Variety of features

Principal Features

• Nanodegree programs
• Suitable for enterprises
• Paid certificates of completion

Pros

• Easy to navigate
• No technical issues
• Seems to care virtually its users

Main Features

• Huge diversity of courses
• 30-day refund policy
• Free certificates of completion

Pros

• Bully user experience
• Offers quality content
• Very transparent with their pricing

Chief Features

• Gratuitous certificates of completion
• Focused on information scientific discipline skills
• Flexible learning timetable

As a Method

Functions can be defined equally object methods in JavaScript.

The example below creates a new object simpleObject with two properties (numberX and numberY) and one method (sumNumbers):

Example

                              var                simpleObject = {                numberX:                58,                numberY:                11,                sumNumbers:                                  function                  ()                {                return                this.numberX +                this.numberY;   } } simpleObject.sumNumbers();// Will render 69                          

The sumNumbers role is within of the simpleObject object and is endemic by it. Therefore, if we call sumNumbers part, it will return the value of this. The value will turn out to be object: sumNumbers function is owned by an object, which is simpleObject:

Example

                              var                simpleObject = {                numberX:                58,                numberY:                11,                sumNumbers:                                  function                  ()                {                return                this;     } } simpleObject.sumNumbers();                // returns [object Object]  (the simpleObject)                          

Using a Office Constructor

Constructor invocation is achieved if the function declaration starts with new keyword. It works similar creating a new function, but as functions are objects in JavaScript, you create an object.

When an object is created using the constructor, it inherits all its backdrop and methods:

Example

                              // This is the constructor                                  function                  simpleConstructor(num1, num2)                {                this.number1 = num1;                this.number2  = num2; }                // Creating a new object                var                xyz =                new                simpleConstructor(14,                8); xyz.number2;                // would render 8                          

Using a Function Method

JavaScript has predefined call() and employ() methods. Both of them can invoke other functions, and have to take their owner as the start argument.

The only difference betwixt these methods is that while call() method takes arguments 1 by 1 separately, utilize() method takes arguments as an array:

Example

                                                role                  simpleFunction(x, y)                {                return                x * y;   }  simpleObject = simpleFunction.call(simpleObject,                22,                2);                // Volition return 44                          

Example

                                                part                  simpleFunction(x, y)                {                render                10 * y;   } newArray = [22,                2];                // Will also return 44                simpleObject = simpleFunction.use(simpleObject, newArray);            

JavaScript Call Function: Summary

• Knowing how to call a function in JavaScript means understanding all possible options: function, method, office constructor, and role method. How a function should be invoked, depends on the context.
• When working with functions, you should know ever exist aware of what this keyword references in a item example.

lairdevinly.blogspot.com

Source: https://www.bitdegree.org/learn/javascript-call-function

Share this post