根据项目的属性在javascript对象中查找项目

Question

Say I have an object like this:

var things = { 
    "First Item": {"name": "First Item", "url":"firstitem" },
    "Second Item": {"name": "Second Item", "url":"seconditem" }
};

I want to be able to check if any of the object values have a url value of "firstitem", and if so, retrieve all of the values associated with that item (for "name" and "url"). How would one go about making a loop to accomplish this?

Answer 1

var things = { 
    "First Item": {"name": "First Item", "url":"firstitem" },
    "Second Item": {"name": "Second Item", "url":"seconditem" }
};

Object.keys(things).
    filter(k => things[k].url === "firstitem").
    map(k => things[k])
// [ { name: 'First Item', url: 'firstitem' } ]

Answer 2

There are 2 ways to loop over this. You can use the foreach method:

for (var key in things) {
    things[key].url; // do thing with this
}

Or the Object.keys method

Object.keys(things); // Returns an array of ["First Item", "Second Item"]

I prefer the second, because for your use case you can do this:

Object.keys(things).find(elem => things[elem].url === "seconditem");

This will return undefined if it isn't found, or in the case above, it will return {"name": "Second Item", "url": "seconditem" }
You can also use findIndex in place of find, which will get you the index of it in the array returned by Object.keys()

For more details:

• Object.keys() https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
• Array.prototype.find() https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find
• Array.prototype.findIndex() https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex