How to remove global “use strict” added by babel

Question

I\'m using function form of \"use strict\" and don\'t want global form which Babel adds after transpilation. The problem is I\'m using some libraries that aren\'t using \"us

Answer 1

Babel 5

You'd blacklist "useStrict". For instance here's an example in a Gruntfile:

babel: {
    options: {
        blacklist: ["useStrict"],
        // ...
    },
    // ...
}

Babel 6

Since Babel 6 is fully opt-in for plugins now, instead of blacklisting useStrict, you just don't include the strict-mode plugin. If you're using a preset that includes it, I think you'll have to create your own that includes all the others, but not that one.

Answer 2

Personally, I use the gulp-iife plugin and I wrap IIFEs around all my files. I noticed that the babel plugin (using preset es2015) adds a global "use strict" as well. I run my post babel code through the iife stream plugin again so it nullifies what babel did.

gulp.task("build-js-source-dev", function () {
	return gulp.src(jsSourceGlob)
      .pipe(iife())
	  .pipe(plumber())
	  .pipe(babel({ presets: ["es2015"] }))// compile ES6 to ES5
	  .pipe(plumber.stop())
      .pipe(iife()) // because babel preset "es2015" adds a global "use strict"; which we dont want
      .pipe(concat(jsDistFile)) // concat to single file
	  .pipe(gulp.dest("public_dist"))
});

Answer 3

Please use "es2015-without-strict" instead of "es2015". Don't forget you need to have package "babel-preset-es2015-without-strict" installed. I know it's not expected default behavior of Babel, please take into account the project is not mature yet.

Answer 4

I just made a script that runs in the Node and removes "use strict"; in the selected file.

file: script.js:

let fs = require('fs');
let file = 'custom/path/index.js';
let data = fs.readFileSync(file, 'utf8');
let regex = new RegExp('"use\\s+strict";');
if (data.match(regex)){
    let data2 = data.replace(regex, '');
    fs.writeFileSync(file, data2);
    console.log('use strict mode removed ...');
}
else {
    console.log('use strict mode is missing .');
}

node ./script.js