javascript - Vue equivalent of setTimeout?

Question

I'm making a shopping cart system with Laravel and Vue. When I add an item to the basket, I display a confirmation message by toggling a Vue variable being watched by a v-if:

<div class="alert alert-success" v-if="basketAddSuccess" transition="expand">Added to the basket</div>

And the JS:

addToBasket: function(){
                item = this.product;
                this.$http.post('/api/buy/addToBasket', item);
                this.basketAddSuccess = true;
            }

(And yes, I will be adding this in a then-catch shortly).

This works fine and the message appears. However, I'd like the message to disappear again after a certain time, say a few seconds. How can I do this with Vue? I've tried setTimeOut but Vue doesn't seem to like it, saying it's undefined.

EDIT: I was misspelling setTimeout like an idiot. However, it still doesn't work:

My function is now:

addToBasket: function(){
                item = this.photo;
                this.$http.post('/api/buy/addToBasket', item);
                this.basketAddSuccess = true;
                setTimeout(function(){
                    this.basketAddSuccess = false;
                }, 2000);
            }

Answer 1

Arrow Function

The best and simplest way to solve this problem is by using an arrow function () => {}:

    addToBasket() {
        var item = this.photo;
        this.$http.post('/api/buy/addToBasket', item);
        this.basketAddSuccess = true;
        // now 'this' is referencing the Vue object and not the 'setTimeout' scope
        setTimeout(() => this.basketAddSuccess = false, 2000);
    }

This works because the this of arrow functions is bound to the this of its enclosing scope- in Vue, that's the parent/ enclosing component. Inside a traditional function called by setTimeout, however, this refers to the window object (which is why you ran into errors when you tried to access this.basketAddSuccess in that context).

Argument Passing

Another way of doing this would be passing this as an arg to your function through setTimeout's prototype using its setTimeout(callback, delay, arg1, arg2, ...) form:

    addToBasket() {
        item = this.photo;
        this.$http.post('/api/buy/addToBasket', item);
        this.basketAddSuccess = true;
        //Add scope argument to func, pass this after delay in setTimeout
        setTimeout(function(scope) {
             scope.basketAddSuccess = false;
        }, 2000, this);
    }

(It's worth noting that the arg passing syntax is incompatible with IE 9 and below, however.)

Local Variable

Another possible, but less eloquent and less encouraged, way is to bind this to a var outside of setTimeout:

    addToBasket() {
        item = this.photo;
        this.$http.post('/api/buy/addToBasket', item);
        this.basketAddSuccess = true;
        //Declare self, which is accessible inside setTimeout func
        var self = this;
        setTimeout(function() {
             self.basketAddSuccess = false;
        }, 2000);
    }

Using an arrow function would eliminate the need for this extra variable entirely however, and really should be used unless something else is preventing its use.