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Do we need to put "use strict" in external js files if our html file (which imports the external js files) already has "use strict" ?
And if our external js files do not have "use strict", are they still "strict" within a HTML file that has "use strict" ?
Example:
<!DOCTYPE html>
<html>
<head>
<title></title>
<script>
"use strict";
function f() {
// calling File1 functions (File1 does not have "use strict"; at the top)
// are the File1 functions "strict"?
}
</script>
<script src="File1.js"></script>
<script>
//by the way.. is it strict here ?
</script>
</head>
<body>
</body>
</html>
385
First, all of your code absolutely should be run in strict mode. Core modern javascript functionality is changed (see . call() and apply()) or disfigured (silent Errors) by executing code outside of strict mode.
JavaScript in <head> or <body> You can place any number of scripts in an HTML document. Scripts can be placed in the <body> , or in the <head> section of an HTML page, or in both.
To include an external JavaScript file, we can use the script tag with the attribute src . You've already used the src attribute when using images. The value for the src attribute should be the path to your JavaScript file. This script tag should be included between the <head> tags in your HTML document.
JavaScript in External FileThe script tag provides a mechanism to allow you to store JavaScript in an external file and then include it into your HTML files.
You must put "use strict"; (or 'use strict';) at the top of each script (or function) to make them strict. In your example, the functions in File1.js will not be strict, nor will the second block. See https://developer.mozilla.org/en/JavaScript/Strict_mode#Invoking_strict_mode for details.
If this wasn't the case, using strict mode could invalidate third-party scripts that you import, so it makes sense that strictness only applies to the scripts and individual functions that you explicitly specify.
For example:
external.js:
console.log("C: This script is non-strict.");
var g = function (x) {
console.log("g is non-strict regardless of caller.");
return 2 * x;
};
test.html:
<!DOCTYPE html>
<html>
<head>
<title></title>
<script>
"use strict";
console.log("A: This script element is strict.");
function f() {
console.log("The strictness of a script does not affect" +
" the strictness of external scripts, so g is" +
" still non-strict when called from f.");
return g(3);
}
</script>
<script src="external.js"></script>
<script>
f();
console.log("B: This script element is non-strict.")
</script>
</head>
<body>
</body>
</html>
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