Javascript strict program
Rajeev Ranjan Tiwari
JavaScript Use Strict
use strict"; Defines that JavaScript code
(2)
<!DOCTYPE html>
<html>
<body>
<h2>Global "use strict" declaration.</h2>
<p>Activate debugging in your browser (F12) to see the error report.</p>
<script>
"use strict";
myFunction();
function myFunction() {
y = 3.14; // This will cause an error (y is not defined)
}
</script>
</body>
</html>
(3)
<!DOCTYPE html>
<html>
<body>
<p>"use strict" in a function will only cause errors in that function.</p>
<p>Activate debugging in your browser (F12) to see the error report.</p>
<script>
x = 3.14; // This will not cause an error.
myFunction();
function myFunction() {
"use strict";
y = 3.14; // This will cause an error (y is not defined).
}
</script>
</body>
</html>
executed in "strict mode".
The "use strict" Directive
The "use strict" directive was new in ECMAScript version 5.
It is not a statement, but a literal expression, ignored by earlier versions of JavaScript.
The purpose of "use strict" is to indicate that the code should be executed in "strict mode".
With strict mode, you can not, for example, use undeclared variables.
All modern browsers support "use strict" except Internet Explorer 9 and lower:
The numbers in the table specify the first browser version that fully supports the directive.
You can use strict mode in all your programs. It helps you to write cleaner code, like preventing you from using undeclared variables.
"use strict" is just a string, so IE 9 will not throw an error even if it does not understand it.
Declaring Strict Mode
Strict mode is declared by adding "use strict"; to the beginning of a script or a function.
Declared at the beginning of a script, it has global scope (all code in the script will execute in strict mode):
(1)
<!DOCTYPE html>
<html>
<body>
<h2>With "use strict":</h2>
<h3>Using a variable without declaring it, is not allowed.</h3>
<p>Activate debugging in your browser (F12) to see the error report.</p>
<script>
"use strict";
x = 3.14; // This will cause an error (x is not defined).
</script>
</body>
</html>
प्रिय पाठकों, मै आशा करता हूँ की आपको हमारी यह पोस्ट बहुत पसंद आया होगा। अगर आपको यह पोस्ट अच्छा लगा हो तो इसे जरुर अपने दोस्तों के साथ शेयर करे।
Thanks friend posted by Rajeev Ranjan Tiwari
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