当一种方法依赖于另一种方法

Question

What is the best way to deal with the following situation in JavaScript.

I have three methods ( m1 , m2 , m3 ) and the last one ( m3 ) depends from the results of the others two ( m1 , m2 ).

In this way it works, but I am curious to know if there is a better way to write the code in this situation, especially for future developers that will read the code.

var O = function () {
    this.p = 0;
}

O.prototype.makesomething = function () {
    var that = this;
    that.m1();
    that.m2();
    that.m3();
}

O.prototype.m1 = function () {O.p++}; // it changes the value O.p
O.prototype.m2 = function () {O.p++}; // it changes the value O.p
O.prototype.m3 = function () {return O.p}; // m3 depends by m1, m2 because it needs to get the update value of O.p

Answer 1

First, I don't know for sure, but putting this.p = 0 inside O does not make sense in combination with Op . You probably mean this.p inside m3 , when referring to the instance.

Anyway, if you are looking for readability, you could make some simple but idiomatic functions like this: http://jsfiddle.net/ZvprZ/1/ .

var O = function () {
    this.p = 0;
}

O.prototype.makesomething = function () {
    var that = this;

    var result = when( that.m1(), that.m2() )
                .then( that.m3() );

    return result;
}

O.prototype.m1 = function () {this.p++};
O.prototype.m2 = function () {this.p++};
O.prototype.m3 = function () {return this.p};

The when / then can be rather straight-forward since it does not do anything than making it more readable:

(function(window) {
    var when, then, o;

    when = function() {
        return o; // just return the object so that you can chain with .then,
                  // the functions have been executed already before executing
                  // .when
    };

    then = function(a) {
        return a; // return the result of the first function, which has been
                  // executed already (the result is passed)
    };

    o = { when: when,
          then: then };

    window.when = when; // expose
    window.then = then;
})(window);