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call怎么读英语

call怎么读英语

Introduction

'.call' is a method in JavaScript that is used to call a function with a specified 'this' value and arguments provided individually. Proper understanding of '.call' is essential for writing efficient and effective code in JavaScript. In this article, we will delve deeper into what '.call' does and how it can be used.

What is '.call'?

'.call' is a method that is used to call a function with a specified 'this' value and arguments provided individually. It is one of the many methods available in JavaScript to call a function.

The basic syntax of using '.call' is as follows:
functionName.call(thisValue, arg1, arg2, arg3,...)

How '.call' Works?

When '.call' method is used to call a function, it assigns the value of 'this' to the specified 'thisValue'. If 'thisValue' is not specified or is set to 'null' or 'undefined', the global object will be used as the 'thisValue'.

The arguments provided after 'thisValue' are passed as individual arguments to the function being called. The order of the arguments must match the order of parameters in the function definition. If the function does not expect any arguments, '.call' can be called without any arguments after the 'thisValue'.

Benefits of Using '.call'?

There are several benefits of using '.call' in JavaScript. One of the major benefits is that it allows you to call a method belonging to one object, but with another object assigned to 'this'.

Another benefit of using '.call' is that it allows you to reuse code by borrowing methods from other objects that share the same properties and methods. This can result in cleaner and more efficient code by eliminating the need for duplicating code.

Example of Using '.call'

Here is an example of how '.call' can be used in JavaScript:

const person1 = { firstName: 'John', lastName: 'Doe', fullName: function() { return this.firstName + ' ' + this.lastName; }}const person2 = { firstName: 'Mary', lastName: 'Jane'}const person2FullName = person1.fullName.call(person2); //Mary Jane

Conclusion

'.call' method is a powerful tool in JavaScript that allows you to call a function with a specified 'this' value and arguments provided individually. It has several benefits such as allowing you to reuse code and borrowing methods from other objects. By better understanding how '.call' works and how to use it effectively, you can write more efficient and effective code in JavaScript.