filtering an array of objects by an array of strings

Question

I'm filtering an array of objects with the following code:

  filterCategory(category: [string]) {
    this.projects = this.projects.filter(project => project.category == category);
  }

It works to a degree but I want to refine it so it will return any object that has the category string within.

e.g.

project: [{
    name: "thing1"
    category: ["Design", "Web Design"]
  }, {
    name: "thing2"
    category: ["Web Design"]
  }, {
    name: "thing3"
    category: ["Design"]
  }, {
    name: "thing4"
    category: ["Design", "Web Design"]
  }]

filterCategory("Design")

filterCategory design currently will only return thing3 but I'd like it to return thing1, thing3, and thing4.

silentsod · Accepted Answer · 2016-11-02 00:01:28Z

2

JavaScript's Array.indexOf will look at each array value for a match.

project => project.category.indexOf(category) !== -1

answered Nov 2, 2016 at 0:01

silentsod

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2 Comments

Jleibham Over a year ago

this worked! would you mind explaining what the -1 does at the end of the code?

silentsod Over a year ago

The indexOf function returns -1 if the value is not found, since you're looking for matches you need to check that the return value is not -1. > -1 would be another equivalent means of performing the check.

Adrian Brand · Accepted Answer · 2016-11-01 23:58:12Z

1

project => {
    for (let i = 0; i < project.category.length; i++) {
        if (project.category[i] === category) {
            return true;
        }
    }
    return false;
}

answered Nov 1, 2016 at 23:58

Adrian Brand

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Comments

Jleibham · Accepted Answer · 2016-11-03 15:29:00Z

0

I found another (less code) way to do this with ES6. Instead of project => project.category.indexOf(category) !== -1 you can use .includes to do the same thing so the final code would look like this:

project => project.category.includes(category)

Worked the same for me just a little cleaner if you're using ES6.

answered Nov 3, 2016 at 15:29

Jleibham

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