Javascript：使用第二个数组中的值提取数组中的密钥对值

Question

I have a shortlist array that I wish to use to extract the numerical value for the corresponding months from the seasons array.

var shortlist = [ "dec", "jan", "feb" ];

var seasons = [{ "jan": "0", "feb": "0", "mar": "0", "apr": "0", "may": "2", "jun": "1", "jul": "1", "aug": "1", "sep": "2", "oct": "0", "nov": "0", "dec": "0" }];

As each value is extracted it will be used for some additional functions.

Answer 1

Try using Array#map :

 var shortlist = [ "dec", "jan", "feb" ]; var seasons = [{ "jan": "0", "feb": "0", "mar": "0", "apr": "0", "may": "2", "jun": "1", "jul": "1", "aug": "1", "sep": "2", "oct": "0", "nov": "0", "dec": "0" }]; const result = shortlist.map(e => +seasons[0][e] || 0); console.log(result);

But if you have multiple objects in seasons array, try it like this, it will give you nested arrays:

 var shortlist = [ "dec", "jan", "feb" ]; var seasons = [ { "jan": "0", "feb": "0", "mar": "0", "apr": "0", "may": "2", "jun": "1", "jul": "1", "aug": "1", "sep": "2", "oct": "0", "nov": "0", "dec": "0" }, { "jan": "2", "feb": "0", "mar": "0", "apr": "0", "may": "2", "jun": "1", "jul": "0", "aug": "1", "sep": "0", "oct": "0", "nov": "0", "dec": "1" }, ]; const result = seasons.map(s => shortlist.map(e => +s[e] || 0)); console.log(result);

Answer 2

 var shortlist = ['dec', 'jan', 'feb']; var seasons = [ { jan: '0', feb: '0', mar: '0', apr: '0', may: '2', jun: '1', jul: '1', aug: '1', sep: '2', oct: '0', nov: '0', dec: '0' } ]; const nums = shortlist.map((mon) => seasons[0][mon]); console.log(nums);