如何在嵌套数组中的键值对中输出键

Question

Inside the array of item, there's an array with with the name 'folder'and inside the array there's 'info' How can I be able to print only the keys and not the value from the info array? as in print out 'created' and 'modified" ?

 let item = [ { itemName: 'folder', info: { created:'August 13 2013', modified: 'December 06 2017' } }, { itemName: 'new folder', info: 'ruby files' }, { itemName: 'documents', info: '' } ] 

Answer 1

您可以通过循环数组来打印对象键，并使用Object.keys()来打印键

Answer 2

Check each item with forEach and if an item's info property is an object, print its keys.

item.forEach(data => {
  if(data.info.constructor === Object) {
    console.log(Object.keys(data.info));
  }
})

Answer 3

look at each property and use a recursing function to go deeper :

  let item = [
  {
    itemName: 'folder',
    info:
    {
      created:'August 13 2013',
      modified: 'December 06 2017'
    }
  },
  {
    itemName: 'new folder',
    info: 'ruby files'
  },
  {
    itemName: 'documents',
    info: ''  
  }
];

var console=window.console;

function displayObj(obj) {
    if (obj instanceof Array) {
        for (var i = 0; i < obj.length; i++) {
            console.log('obj['+i+']='+obj[i]);
            displayObj(obj[i]);
        }

    }
    if (obj instanceof Object) {
        for (var p in obj) {
            console.log('obj.'+p+'='+obj[p]);
            displayObj(obj[p]);
        }
    }
}

displayObj(item);

Answer 4

Well, it's not infinitely recursive, but it works (i'll try to ameliorate it)

let items = [
    {
        itemName: 'folder',
        info:
        {
            created:'August 13 2013',
            modified: 'December 06 2017'
        }
    },
    {
        itemName: 'new folder',
        info: 'ruby files'
    },
    {
        itemName: 'documents',
        info: ''    
    }
];

let Keys = [];

items.forEach((el, index) => {
    Object.keys(el).forEach(key => {
        if(!Keys[index])
            Keys[index] = [];
        if(typeof el[key] === 'object'){
            Keys[index].push(Object.keys(el[key]));
        }
        else {
            Keys[index].push(key);
        }
    })
});

JSFiddle