javascript在应用新的对象之前删除对象的先前过滤器

Question

I have a series of buttons that apply filters to an object using a function similar to this:

isNew(type) {
    //need to reset filter first
    this.results = this.results.filter(function(type) {
        return type.has_user_viewed === true
    })
    console.log('isNew');

}

The problem I have is if one filter is applied by the user clicking, and then another filter applied, the filtered array is filtered again. What I need to do with the above is reset the object to it's original state before applying a new filter. Not sure how to "reset" a filter here?

Answer 1

Just save the unfiltered data to a variable. filter creates a new array object (shallow copying elements) each time, so your code overwrites the original data with the filtered data:

this.data = [...whatever the source is]
isNew(type) {
    //need to reset filter first
    this.results = this.data.filter(function(type) {
        return type.has_user_viewed === true
    })
    console.log('isNew');

}

Answer 2

You'll probably need to store the result of the filter somewhere other than this.results if you want to access the original list of results for additional filtering later. Note that this change will likely force you to change other code.

An example of what I'm recommending:

this.filteredResults = this.results.filter(function(type) {
    return type.has_user_viewed === true
})

I would suggest that you google immutability, as understanding it will help you greatly when you need to solve similar problems in the future.