Methods and advantages of implementing use strict in JavaScript

This tutorial will discuss theuse strictFeatures. Here, we will learn how to create and execute in JavaScript code statements through different examples.use strictKeywords.

Use strict in JavaScript

In JavaScript version ECMAScript 5, Strict Mode is a new feature introduced that will help us execute a set of programs and their functions in a strict operational context. ususe strictThe context to limit various operations and throw more exceptions.

We pass the statementuse strictInstruct the browseruse strictmodel. It is the smallest and safer feature set of JavaScript.

Implement use strict in JavaScript

Remember, we cannot use strict mode for block statements enclosed in braces. The following are two methods of use strict mode:

We can use it globally throughout the script.
We can use it in individual functions.

Implement use strict for the entire script in JavaScript

Before any other statement, we will have the exact statementuse strictUsed to call strict mode for the entire script.

grammar:

//strict mode syntax for Whole-script
'use strict';
let a = "script for strict mode!";

Implement use strict for a single function in JavaScript

In the function body, before any other statement, we will have the exact statementuse strictStrict mode used to call functions.

grammar:

function strictFunction() {
    // strict mode syntax for Function
    'use strict';
    function nestedFunction() { return 'Javascript on DelftStack'; }
    return "strict mode functions!  " + nestedFunction();
}
function notStrictFunction() { return "non strict function"; }

Strict mode example

As we all know, typing in the variable name incorrectly creates a new global variable in plain JavaScript. In strict mode, it throws an error.

example:

<!DOCTYPE html>
<html>
<body>
    <p>function will cause errors while using `use strict` in that function.</p>
    <p>To see the error reprt just activate debugging in your browser by pressing (F12).</p>
    <script>
        a = 10;    // This will not cause an error.
        myFunction();
        function myFunction() {
            "use strict";
            b = 10;  // This will cause an error (b is not defined).
        }
    </script>
</body>
</html>

We defined it in the source code of this HTML page<script>Tags to use JavaScript code statements. exist<script>In the tag, we simply use the numeric value 10 to initialize undefined variablesaAnd callmyFunction()。

After that, we useuse strictKeyword createdmyFunction()Statement. We also initialized the undefined variable with the value 10.b, inuse strictTest execution in mode.

You can use the .html extension to save the given HTML example and open it in any browser to check the output. You need to activate the debug mode of the browser, just pressF12You can view the error report.

Output:

the function will cause errors while using `use strict`.

To see the error report, activate debugging in your browser by pressing (F12).

Advantages of implementing use strict in JavaScript

In simple JavaScript semantics, strict patterns are changed in various ways. We can eliminate some silent errors in JavaScript by changing them to throwing errors by using strict mode.

To perform optimizations, we can fix bugs that make the JavaScript engine difficult to handle.
Strict mode code can sometimes execute faster than normal code, which is not available in strict mode.
In future versions of ECMAScript, strict mode prevents certain syntaxes that may be defined.
Strict mode prevents any unsafe operations, such as attempting to access global variables or objects.
Strict mode disables confusing features or underconsidered features.
To write secure JavaScript more efficiently, we use strict patterns.

This is the end of this article about how to implement use strict in JavaScript. For more related content on JS implementation of use strict, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!