Javascript对象数组：返回值的最佳方法？

Question

I have an array of objects in Javascript with two keys with this structure:

"data": [
  {
  "description": "Unknown",
  "type": 0
  },
  {
  "description": "On",
  "type": 1
  },
  {
  "description": "Off",
  "type": 2
  },
  ...
  ]

I want to pass it a 'type' numeric value and if it finds it in the array, returns me the description value. For example, if I pass '0', I want it to return 'Unknown'.

This is easily done with a for or forEach loop, but there is an inbuilt function in JS that lets me do it in a single line?

Answer 1

You could use either find

 var data = [{ description: "Unknown", type: 0 }, { description: "On", type: 1 }, { description: "Off", type: 2 }]; console.log(data.find(({ type }) => type === 1).description); 

or for faster access use a hash table for the types

 var data = [{ description: "Unknown", type: 0 }, { description: "On", type: 1 }, { description: "Off", type: 2 }], types = Object.assign(...data.map(({ type, description }) => ({ [type]: description }))); console.log(types[1]); 

or a Map

 var data = [{ description: "Unknown", type: 0 }, { description: "On", type: 1 }, { description: "Off", type: 2 }], types = data.reduce((m, { type, description }) => m.set(type, description), new Map); console.log(types.get(1)); 

Answer 2

In one liner you can Filter the list.

 var obj=[{ "description": "Unknown", "type": 0 }, { "description": "On", "type": 1 }, { "description": "Off", "type": 2 }]; var filterType=1; console.log(obj.filter(e=>e.type == filterType)[0]['description']) 

Answer 3

Have a look at the attached code snippet , which gives the desired output.

• Find function to itreat throughout your array to match the condition ie in this case the passedIndex to check whether it is present in list

• If present return the item

 var list = [{ "description": "Unknown", "type": 0 }, { "description": "On", "type": 1 }, { "description": "Off", "type": 2 } ]; function findItem(index) { var result = list.find(function(item) { if (item.type == index) { return item; } }); return result.description; } var description = findItem(2); console.log('The Description is "' + description + '"') 

.