How to get a variable from another file in gruntfile - gruntjs

Question

I am new to grunt.
My requirement is that I need to uglify my files based on the variable set on another file.
Let's say I have some abc.js file in which I have a variable var is_uglify = true;
I need to read the value of the variable in gruntfile and perform the build accordingly.
If variable is true, I need to do:
grunt.registerTask('build', ['clean:build','uglify']);
otherwise
grunt.registerTask('build', ['clean:build']);
Can anyone help with this?

Answer 1

This can be achieved by:
Defining a Custom Task - namely getValue in the gist below.
In the getValue Task/Function utilize grunt.file.read to obtain the contents of abc.js.
Then use a regex to match the Boolean value assigned to the variable is_uglify.
Once the Boolean value for is_uglify is obtained then conditionally run either the registered Task named buildA or buildB using grunt.task.run
Gruntfile.js
The following gist shows how this can be achieved:
module.exports = function (grunt) {
'use strict';
grunt.initConfig({
uglify: {
// ... <-- Define as necessary.
},
clean: {
build: {
//... <-- Define as necessary.
}
}
});
grunt.registerTask('getValue', 'Gets the value of a variable', function () {
var filepath = "path/to/abc.js", // <-- Define as necessary.
content = grunt.file.read(filepath),
value = content.match(/(?:var is_uglify = )(true|false);/);
if (!value) {
grunt.fail.warn(
'\'var is_uglify = [true|false];\' not found in: ' + filepath['yellow']
)
}
if (value[1] === 'true') {
grunt.task.run(['buildA']);
} else {
grunt.task.run(['buildB']);
}
});
grunt.loadNpmTasks('grunt-contrib-uglify');
grunt.loadNpmTasks('grunt-contrib-clean');
grunt.registerTask('build', ["getValue"]);
grunt.registerTask('buildA', ['clean:build','uglify']);
grunt.registerTask('buildB', ['clean:build']);
};
Additional Notes
In the following line of code the "path/to/abc.js" part will need to be redefined as per your directory structure. This must be the path to your file containing var is_uglify = ...;:
var filepath = "path/to/abc.js",
An explanation to the regex pattern /(?:var is_uglify = )(true|false);/ can be found here. It will find the first match only in abc.js.
The getValue Task/Function will warn if the is_uglify variable is missing and the Task/function simply fails and returns early.
After you have defined the configuration for the uglify and clean:build Task run $ grunt build via your CLI.