Javascript-如何获取数组中的第一个元素？

Question

Example:

var myArray = ['e', {pluribus: 'unum'}];

How do I get the first 'e'?

My actual array looks like this:

({'U.S., MCC':{score:"88.88", url:"http://ati.publishwhatyoufund.org/donor/usmcc/"}, GAVI:{score:"87.26", url:"http://ati.publishwhatyoufund.org/donor/gavi/"}, 'UK, DFID':{score:"83.49", url:"http://ati.publishwhatyoufund.org/donor/ukdfid/"}, UNDP:{score:"83.38", url:"http://ati.publishwhatyoufund.org/donor/undp/"}, 'World Bank, IDA':{score:"73.81", url:"http://ati.publishwhatyoufund.org/donor/world-bank-ida/"}, 'Global Fund':{score:"70.65", url:"http://ati.publishwhatyoufund.org/donor/global-fund/"}}) 

I need to get the name. ie 'US, MCC' and then the score and the url - I am using this in highcharts as data points in a graph.

I know it should be simple, but I am a complete JS noob.

Thanks

Answer 1

To get the first element from your array, just use this:

myArray[0]

Notice that 0 points at the first element in the array. Arrays are zero-indexed.

Have a look at this mdn page about arrays to learn more.

---

However , what you have there isn't an array, it's an object. You can't access those with numeric keys (like 0, 1, 2 etc)

To get the first element of your object, you have to use the "key" to access that value.
Assuming:

var myObject = {'U.S., MCC':{score:"88.88", url:"http://ati.publishwhatyoufund.org/donor/usmcc/"}, GAVI:{score:"87.26", url:"http://ati.publishwhatyoufund.org/donor/gavi/"}, 'UK, DFID':{score:"83.49", url:"http://ati.publishwhatyoufund.org/donor/ukdfid/"}, UNDP:{score:"83.38", url:"http://ati.publishwhatyoufund.org/donor/undp/"}, 'World Bank, IDA':{score:"73.81", url:"http://ati.publishwhatyoufund.org/donor/world-bank-ida/"}, 'Global Fund':{score:"70.65", url:"http://ati.publishwhatyoufund.org/donor/global-fund/"}}

Then:

myObject['U.S., MCC']

Will be:

{score:"88.88", url:"http://ati.publishwhatyoufund.org/donor/usmcc/"}

Or, as a more simple example:

var foo = {
    'bar': 1,
    'wut': {'nested': 'you can nest objects! (and arrays, etc)'}
    baz: 'Objects, woo!',  // Quotes around keys aren't mandatory, unless you have
}                          // spaces in the keys: 'quotes mandatory'

foo['bar']     // 1
foo.wut.nested // 'you can nest objects! (and arrays, etc)'
foo.baz        // 'Objects, woo!' (you don't have to use the square brackets,
               //                  if the key is a simple string (No spaces))

Have a look at this mdn article about working with objects to learn more about those.

---

Now, to actually get the "first" element in that object is tricky, since objects aren't sorted. (Even though they may appear so.)

You can loop through an object using a for...in , but there's no guarantee the items will show up in the same order, on different browsers:

for (var key in myObject) {
    if (myObject.hasOwnProperty(key)) { // Make sure it's a proper element on the object, not a prototype function.
        // key == ''U.S., MCC', for example,
        doSomethingWith(myObject[key]);
    }
}

You can iterate over objects in a sorted order, but there's some better answers out there about that.

Answer 2

Try to use this case:

var myObj = {'U.S., MCC':{score:"88.88", url:"http://ati.publishwhatyoufund.org/donor/usmcc/"}, GAVI:{score:"87.26", url:"http://ati.publishwhatyoufund.org/donor/gavi/"}, 'UK, DFID':{score:"83.49", url:"http://ati.publishwhatyoufund.org/donor/ukdfid/"}, UNDP:{score:"83.38", url:"http://ati.publishwhatyoufund.org/donor/undp/"}, 'World Bank, IDA':{score:"73.81", url:"http://ati.publishwhatyoufund.org/donor/world-bank-ida/"}, 'Global Fund':{score:"70.65", url:"http://ati.publishwhatyoufund.org/donor/global-fund/"}};

for(v in myObj) {
    console.log("Obj key: "+v, myObj[v]);
}