Calling function sequentially in vuejs

Question

I am having some problem in vuejs in executing a function/method sequentially. I have three functions like:

MethodA: function(){
    if(x = 1){
        value1 = 2;
    }

    if (x ==2){
         value2 = 4;
    }

    this.MethodB();
}

MethodB: function(){
    Total value = value1 + value2;
}

MethodC: function (){
    this.$http.get('api/getvalue').then(function(response){
        this.set('somedata', response.data);

        response.data.forEach(para){
            if(para.id == 1){
                this.MethodA();
            }
            if(para.id == 2){
                this.MethodA();
            }
        }
    });
}

ready: function(){
    this.MethodC();
}

I would like to execute this.MethodB() only after MethodC and MethodA has completely executed. How can I do this?

I edited your question writing MethodC but now I'm not sure what you meant. Could you please explain how do you expect to have any Method to execute before/after the others if they are circularly dependent on each other? — gurghet
– gurghet, Commented Aug 1, 2016 at 10:43

crabbly · Accepted Answer · 2016-08-01 15:46:49Z

6

You can use Javascript Promises with Vue.js methods:

methodA: function() {
    return new Promise(function(resolve, reject) {
       //run all your methodA code here
       ...

       resolve('MethodA finished');
    });
},
methodB: function() {
    return new Promise(function(resolve, reject) {
       //run all your methodB code here
       ...

       resolve('MethodB finished');
    });
},
methodC: function() {
    //run your methodC code
}

Now, to run methodC only when methodA and methodB are finished, you can use the promises .then and chain them together. For ex:

ready: function() {
    //save `this` to a variable just to make it easier to be accessed within the chain
    let self = this;

    //run methodA, then methodB...only then, methodC
    self.methodA.then(function(resultA) {
        console.log(resultA);
        return self.methodB();
    }).then(function(resultB) {
        console.log(resultB);
        self.methodC();
    });
}

Note: if you running AJAX calls within methodA or methodB, make sure to resolve the promise only when you receive a response. In your ex.:

this.$http.get('api/getvalue').then(function(response){ 
    ...
    resolve('My method is now complete'); 
}

edited Aug 1, 2016 at 15:46

answered Aug 1, 2016 at 15:40

crabbly

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1 Comment

crabbly Over a year ago

@TashiTobgay You are welcome :) Javascript promises are great for async code control.

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