Question

尝试执行以下自定义任务：

'use strict';
module.exports = function(grunt) {
    grunt.initConfig({

        log: {
            one: [1, 2, 3],
            two: "Hello World",
            three: true,
            four: {
                five: function() {
                    grunt.log.writeln("Hi");
                },
                six: function() {
                    grunt.log.writeln("Welcome");
                }
            }
        }

    });
    grunt.registerMultiTask('log', 'Log stuff', function() {
        grunt.log.writeln(this.target + ": " + this.data + "\n");

        if (this.target === 'four') {
            console.log(this.data);

            for(var d in this.data) {
                console.log(this.data['five']());

                console.log(this.data['six']());
            }
        }
    });

    grunt.registerTask('default', 'log');
};

我的输出低于输出：

Running "log:one" (log) task
one: 1,2,3

Running "log:two" (log) task
two: Hello World

Running "log:three" (log) task
three: true

Running "log:four" (log) task
four: [object Object]

{ five: [Function], six: [Function] }
Hi
undefined
Welcome
undefined
Hi
undefined
Welcome
undefined

Done, without errors.

执行第五和第六功能时我无法理解;它用＆＃34; undefined＆＃34;显示正确的输出。从哪里来的未定义？

Answer 1

当你写console.log(this.data['five']());时，它意味着“打印出this.data.five定义的函数的返回值，即：

function() {
    grunt.log.writeln("Hi");
}

此函数没有明确的return，因此其返回值为undefined，您的代码将其打印出来。要避免这种情况，请将代码更改为：

for(var d in this.data) {
    this.data['five']();
    this.data['six']();
}

甚至更好，避免重复：

for(var d in this.data) {
    this.data[d]();
}

在grunt任务中使用自定义函数执行未定义

1 个答案: