出现这个问题，请问如何解决，求解

代码如下：

var app = new Vue({

el: '#app',
data: {
    steps: [
        { name: 'Hello Vue!', completed: false },
        { name: 'Hello World!', completed: false }
    ],
    newStep: ''
},
mounted: function(){
    this.fetchSteps();
},
methods: {
    fetchSteps: function(){
        this.$http.get('/tasks/2/steps').then((response) => {
            // success
            Vue.set(this, 'steps', response.body);
        }, (response) => {
            // error
            response.status;
        });
    },
    addStep: function(){
        this.steps.push({ name: this.newStep, completed: false });
        this.newStep = '';
    },
    complete: function(step){
        step.completed = true;
    },
    removeStep: function(step){
        var index = this.steps.indexOf(step);
        this.steps.splice(index, 1);
    },
    editStep: function(step){
        this.removeStep(step);
        this.newStep = step.name;
        this.$refs.newStep.focus();
    },
    toggleComplete: function(step){
        step.completed = false;
    },
    completeAll: function(){
        this.steps.forEach(function(step){
            step.completed = true;
        });
    },
    clearComplete: function(){
        // this.steps = [];k
        this.steps = this.steps.filter(function(step){
            return !step.completed;
        });
    }
},
computed: {
    inProcess: function(){
        return this.steps.filter(function(step){
            if (step.completed == false) return step;
        })
    },
    processed: function(){
        return this.steps.filter(function(step){
            if (step.completed == true) return step;
        })
    },
    completions: function(){
        return this.steps.filter(function(step){
            return step.completed;
        });
    },
    remaings: function(){
        return this.steps.filter(function(step){
            return !step.completed;
        });
    }
}

})