grunt.yaml

config:

    sass:
        build:
            files:
                static/css/style/css: client/sass/main.sass

    componentbuild:
        build:
            src: .
            dest: ./static/js/
            options:
                standalone: true

    jshint:
        build:
            src:
                - client/js/**/*.js
            options:
                jshintrc: true

    watch:
        options:
            livereload: true
        component:
            files:
                - client/js/**/*.js
                - component.json
            tasks: componentbuild
        sass:
            files:
                - client/sass/**/*.sass
            tasks: sass
            options:
                nospawn: true

npm:
    - grunt-contrib-watch
    - grunt-contrib-sass
    - grunt-contrib-jshint
    - grunt-component-build

tasks:
    build:
        - sass
        - componentbuild
        - jshint
    default:
        - build

gruntfile-yaml.js

// https://github.com/yyx990803/gruntfile-yaml

module.exports = function (grunt) {
    var y = grunt.file.readYAML('grunt.yaml')
    grunt.initConfig(y.config)
    y.npm.forEach(function (t) {
        grunt.loadNpmTasks(t)
    })
    for (var task in y.tasks) {
        grunt.registerTask(task, y.tasks[task])
    }
}

Gruntfile.js

// npm install gruntfile-yaml

// short version:
module.exports = require('gruntfile-yaml')

// or if you still need custom js:
module.exports = function (grunt) {
    require('gruntfile-yaml')(grunt)
    // do your own stuff...
}