对象数组中的 Substring

Question

Using Node.js 10.*

I have the following data structure being returned to me:

const result = [
  {
    ID: 1,
    Reference: 'Id: 123, Name: "first'
  },
  {
    ID: 2,
    Reference: 'Name: "second'
  },
  {
    ID: 3,
    Reference: 'Id: 133, Name: "third'
  }
];

I want to capture the Id of each Reference if it exists, and push to a new array, which would give me the following:

// [123,133]

I can use Filter and Map to filter out which does not contain 'Id' in Reference by the following:

let filter = result.filter(i => i.Reference.includes('Id:')).map(i => i.Reference)

Which gives me:

// ['Id': 123, Name: 'first, 'Id': 133, Name: 'third'] 

So from the array above, I was to just strip out the Id to get:

// [123,133]

Using sub strings doesn't seem to work for me.

Answer 1

Using regex you can strip your number from your string

 const Reference = 'Id: 133, Name: "third' console.log( (/Id:\s(\d+),/g).exec(Reference)[1] );

Final solution:

 const result = [ { ID: 1, Reference: 'Id: 123, Name: "first' }, { ID: 2, Reference: 'Name: "second' }, { ID: 3, Reference: 'Id: 133, Name: "third' } ]; const res = result.map(({Reference})=>+((/Id:\s(\d+),/g).exec(Reference)||[])[1]).filter(item=>.;item) console.log(res);

Answer 2

You could map the part with a regular expression for the digits and return a number.

 const result = [{ ID: 1, Reference: 'Id: 123, Name: "first' }, { ID: 2, Reference: 'Name: "second' }, { ID: 3, Reference: 'Id: 133, Name: "third' }], filter = result.filter(i => i.Reference.includes('Id:')).map(i => i.Reference).map(s => +s.match(/Id:\s*(\d+)/)[1]) console.log(filter);

Answer 3

You can use simple array manipulation if you just extract the portion of text from after Id: (four characters, so up to index 3 in the string) and the first comma that would appear after the number:

 const result = [ { ID: 1, Reference: 'Id: 123, Name: "first' }, { ID: 2, Reference: 'Name: "second' }, { ID: 3, Reference: 'Id: 133, Name: "third' } ]; function extractId(reference) { let from = 3; let to = reference.indexOf(","); return reference.slice(from, to); } let ids = result.filter(i => i.Reference.includes('Id:')).map(i => i.Reference).map(extractId).map(Number); console.log(ids);

Alternatively, you can use a regular expression to capture and extract the ID

 const result = [ { ID: 1, Reference: 'Id: 123, Name: "first' }, { ID: 2, Reference: 'Name: "second' }, { ID: 3, Reference: 'Id: 133, Name: "third' } ]; function extractId(reference) { let regex = /Id: (\d+)/; return reference.match(regex)[1]; } let ids = result.filter(i => i.Reference.includes('Id:')).map(i => i.Reference).map(extractId).map(Number); console.log(ids);