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This article mainly introduces "what is the difference between Const and Object.freeze ()". In daily operation, I believe many people have doubts about the difference between Const and Object.freeze (). The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the questions of "what is the difference between Const and Object.freeze ()"! Next, please follow the editor to study!

Use let

We use let to define variables.

Let APP_NAME = "front-end intelligence @ big change the world" function getApplicationName () {APP_NAME = "who is he?" Return APP_NAME} getApplicationName () / / "who is he?"

In the above example, the function getApplicationName () changes the value of APP_NAME. How can we prevent global variables from being changed?

Use const

We can use const to define it so that the global variable is not changed to?

Const APP_NAME = "front-end intelligence @ big change the world" function getApplicationName () {APP_NAME = "who is he?" Return APP_NAME / / TypeError error will be thrown here}

An attempt to change the value of a variable defined with const results in this error:

Const fruites = ['grape', 'cantaloupe'] fruites.push ('banana') console.log (fruites) / / ["grape", "cantaloupe", "banana"] const constants = {APP_NAME: "frontal intelligence @ big change the world"} constants.APP_NAME = "who is he?" Console.log (constants.APP_NAME) / / who is he?

As you can see from the above two examples, even with const, you can change the value of an array or object.

Const does not use the value of a variable to be immutable, but the reference address of the variable to change.

Now we know that in the case of arrays and objects, we can't change the reference, but we can change the value. How to prevent the values of arrays and objects from being changed?

Use Object.freeze ()

This is where Object.freeze () works, and Object.freeze ignores value changes for objects and arrays.

Let constants = Object.freeze ({APP_NAME: "front-end intelligence @ big change the world"}) constants.APP_NAME = "who is he?" Console.log (constants.APP_NAME) / / "Front end Intelligence @ change the World"

As you can see from the example, if you change the value, it does not throw any errors and does not affect the state of the object.

Object.freeze () prevents changes to the value of an object, but does not prevent changes to references:

Let constants = Object.freeze ({APP_NAME: "Front end Intelligence @ Big change the World"}) constants = {APP_NAME: "Unknown App"} console.log (constants.APP_NAME); / / "Unknown App"

A brief summary:

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Const does not allow you to change the reference to an object or array, but you can change its value.

Object.freeze () ignores value changes for objects or arrays

Combining them together will prevent changes to references and values of objects or arrays

Use const with Object.freeze ()

Const constants = Object.freeze ({APP_NAME: "Coding N Concepts"}); constants.APP_NAME = "Unknown App"; / / this is ignored constants = {APP_NAME: "Unknown App"}; / / this will throw a TypeError

The above example shows that using const in conjunction with Object.freeze () is useful for defining constants and configurations in JS.

At this point, the study of "what is the difference between Const and Object.freeze ()" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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