在Javascript中，是否有一个“如果...发现”的等效项，或者是一种紧凑的方式来执行我想做的事情？

Question

I have an ugly piece of Javascript code

for (var k = 0; k < ogmap.length; ++k)
{
    if (ogmap[k]["orgname"] == curSelectedOrg)
    {
        ogmap[k]["catnames"].push(newCatName);
        break;
    }
} 

Actually, I have a lot of pieces like that in my web app.

I'm wondering if there's a way to make it prettier and compacter. I know there are nice ways of doing this in other languages, like using find_if in C++ ( http://www.cplusplus.com/reference/algorithm/find_if/ ) or FirstOrDefault in C# or fancy LINQ queries in C#.

At the very least, help me make that slightly more readable.

Answer 1

I'd say that you can just write yourself a utility function and then use it whenever necessary.

// finds the first object in the array that has the desired property
// with a value that matches the passed in val
// returns the index in the array of the match
// or returns -1 if no match found
function findPropMatch(array, propName, val) {
   var item;
   for (var i = 0; i < array.length; i++) {
       item = array[i];
       if (typeof item === "object" && item[propName] === val) {
           return i;
       }
   }
   return -1;
}

And, then you can use it like this:

var match = findPropMatch(ogmap, "orgname", curSelectedOrg);
if (match !== -1) {
    ogmap[match]["catnames"].push(newCatName);
}

Answer 2

var find_if = function (arr, pred) {
    var i = -1;
    arr.some(function (item, ind) {
        if (pred(item)) {
            i = ind;
            return true;
        }
    });
    return i;
}

Call it like

var item_or_last = find_if(_.range(ogmap.length), function (item) {
    return item["orgname"] == curSelectedOrg
});

Or without underscore.js

var range = function (a, b) {
    var low = a < b ? a : b;
    var high = a > b ? a : b;
    var ret = [];
    while (low < high) {
        ret.push(low++);
    }
    return ret;  
}
var item_or_last = find_if(range(0, ogmap.length), function (item) {
    return item["orgname"] == curSelectedOrg
});

This lets you declare what you are looking for instead of looping over items and checking each one.