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Sorting an array of object

I wish to sort an array of medals. My first sort returns an array sorted according to the gold medals. I then wish to range those which are having the same gold but silver medals are different (same for bronze). I use the following codes that actually makes me run out of memory. This is my code:
static sort(data) {
let sorted = data.sort((a, b) => b.medal.gold - a.medal.gold);
let next, temp, current;
for (let i = 0; i < sorted.length; i++) {
current = sorted[i].medal;
if (sorted[i+1]) next = sorted[i+1].medal;
if (next) {
if (current.gold === next.gold) {
if (current.silver < next.silver) {
temp = sorted[i+1];
sorted[i+1] = sorted[i];
sorted[i] = temp;
}
else if (current.silver === next.silver) {
if (current.bronze < next.bronze) {
temp = sorted[i+1];
sorted[i+1] = sorted[i];
sorted[i] = temp;
}
}
}
}
}
return sorted;
}

You'll want to improve your compare function so it takes care of that requirement:
data.sort((a, b) => (b.medal.gold - a.medal.gold)
|| (b.medal.silver - a.medal.silver)
|| (b.medal.bronze - a.medal.bronze) )
And then you don't need the (endless) for loop at all.

You have to set next to null somewhere, because it keeps the value from the previous iteration and the if(next) is always true. Afterwards the function will always create one more element and add it in the array (sorted[i+1] = sorted[i]) until you run out of memory.
Here is a working example:
var rawData =
[{ id: 1, medal: {gold: 2, silver: 1, bronze: 1}},
{ id: 2, medal: {gold: 2, silver: 1, bronze: 2} },
{ id: 3, medal: {gold: 5, silver: 1, bronze: 4} } ];
function sortData(data) {
let sorted = data.sort((a, b) => b.medal.gold - a.medal.gold);
let next, temp, current;
for (let i = 0; i < sorted.length; i++) {
next = undefined;
current = sorted[i].medal;
if (sorted[i+1]) next = sorted[i+1].medal;
if (next) {
if (current.gold === next.gold) {
if (current.silver < next.silver) {
temp = sorted[i+1];
sorted[i+1] = sorted[i];
sorted[i] = temp;
}
else if (current.silver === next.silver) {
if (current.bronze < next.bronze) {
temp = sorted[i+1];
sorted[i+1] = sorted[i];
sorted[i] = temp;
}
}
}
}
}
return sorted;
};
console.log(sortData(rawData))
Please note that in the function you are using medal instead of medals as the data you have provided in one of your comments.

Target specific attributes with merge sort

Implemented the merge sort algorithm in my javascript code.
I'm wonder how I can target specific attributes like date, title, name etc for sorting in an array when calling merge sort like mergeSort(array);.
function mergeSort(arr){
var len = arr.length;
if(len <2)
return arr;
var mid = Math.floor(len/2),
left = arr.slice(0,mid),
right =arr.slice(mid);
return merge(mergeSort(left),mergeSort(right));
}
function merge(left, right){
var result = [],
lLen = left.length,
rLen = right.length,
l = 0,
r = 0;
while(l < lLen && r < rLen){
if(left[l] < right[r]){
result.push(left[l++]);
}
else{
result.push(right[r++]);
}
}
return result.concat(left.slice(l)).concat(right.slice(r));
}
Using it in a sort options method. What I want is to print a sorted list. The way the list is sorted will be defined by the users chosen sort option.
function sortConfig(array, sortOption){
if(sortOption == 'title') mergeSort(array.Title);
//..etc
}

To implement the behavior with an optional argument, you could do it in the following way:
function mergeSort(arr, compare = (item => item))
This would set compare function to be the item itself when running the merge
and then we update the calling of the merge and mergeSort itself, where they now all get the compare argument
return merge(mergeSort(left, compare), mergeSort(right, compare), compare);
and ofcourse the declaration for your merge function itself
function merge(left, right, compare)
Which then calls the compare function upon comparison, like here:
if (compare(left[l]) < compare(right[r]))
This lets you choose wether you wish to give an argument or not wen you call your mergeSort function, like:
console.log(mergeSort(nrs).join(','));
console.log(mergeSort(nrs, n => -n).join(','));
console.log(mergeSort(arr, i => i.id));
console.log(mergeSort(arr, i => i.title));
function mergeSort(arr, compare = (item => item)) {
var len = arr.length;
if (len < 2)
return arr;
var mid = Math.floor(len / 2),
left = arr.slice(0, mid),
right = arr.slice(mid);
return merge(mergeSort(left, compare), mergeSort(right, compare), compare);
}
function merge(left, right, compare) {
var result = [],
lLen = left.length,
rLen = right.length,
l = 0,
r = 0;
while (l < lLen && r < rLen) {
if (compare(left[l]) < compare(right[r])) {
result.push(left[l++]);
} else {
result.push(right[r++]);
}
}
return result.concat(left.slice(l)).concat(right.slice(r));
}
var arr = [{
title: 'test 5',
id: 4
}, {
title: 'test',
id: 0
}, {
title: 'test 3',
id: 2
}, {
title: 'test 4',
id: 3
}];
var nrs = [5, 3, 7, 156, 15, 6, 17, 9];
// and call like
console.log(mergeSort(nrs).join(','));
console.log(mergeSort(nrs, n => -n).join(','));
// or like
console.log(mergeSort(arr, i => i.id));
console.log(mergeSort(arr, i => i.title));

For the sake of brevity, these examples show how to sort an array of objects based on a property with a string value. You would most likely need to create some additional logic to handle different types of properties.
1. Array.sort()
You can do this with the Array.sort() method
Fiddle Example
myThings = [
{ alpha: 'a' },
{ alpha: 'x' },
{ alpha: 'p' },
{ alpha: 'orange' },
{ alpha: 'c' },
{ alpha: 'w' }
];
myThings.sort(function(a, b) {
var alphaA = a.alpha.toUpperCase();
var alphaB = b.alpha.toUpperCase();
if (alphaA < alphaB) return -1;
if (alphaA > alphaB) return 1;
return 0;
});
console.log(myThings);
2. Or, compare array item property value instead of array item value
Fiddle Example
function mergeSort(arr, prop) {
if (arr.length < 2)
return arr;
var middle = parseInt(arr.length / 2);
var left = arr.slice(0, middle);
var right = arr.slice(middle, arr.length);
return merge(mergeSort(left, prop), mergeSort(right, prop), prop);
}
function merge(left, right, prop) {
var result = [];
while (left.length && right.length) {
if (left[0][prop] <= right[0][prop]) {
result.push(left.shift());
} else {
result.push(right.shift());
}
}
while (left.length)
result.push(left.shift());
while (right.length)
result.push(right.shift());
return result;
}
myThings = [
{ alpha: 'a' },
{ alpha: 'x' },
{ alpha: 'p' },
{ alpha: 'orange' },
{ alpha: 'c' },
{ alpha: 'w' }
];
console.log(mergeSort(myThings, 'alpha'));

Shortest path algorithm js error

I am quite new into JS and a friend of mine sent me this fiddle
function shortestPath(g, s) {
g.vertexes.forEach(function(u) {
u.dist = Infinity;
u.prev = null;
});
s.dist = 0;
for (var i = 0; i < g.vertexes.length - 1; i++) {
g.edges.forEach(function(e) {
update(e);
});
}
printResult(); }
function update(e) {
var u = e.from;
var v = e.to;
if (v.dist > u.dist + e.data) {
v.dist = u.dist + e.data;
v.prev = u;
} }
var result = [];
function printResult() {
var str = '';
debugger;
for (var i = 0; i < result[0].length; i++) {
for (var j = 0; j < result.length; j++) {
str += result[i][j] + ' ';
}
console.log(str);
str = '';
} }
function printGraph(G) {
var a = [];
G.vertexes.forEach(function(u) {
a.push(u.dist);
});
result.push(a); }
function Graph(options) {
options = options || {};
this.directed = (options.directed != null) ? options.directed : true;
this.vertexes = [];
this.edges = []; }
Graph.prototype.vertex = function(name) {
var v = {
adjacent: [],
name: name.toString()
};
this.vertexes.push(v);
return this; };
Graph.prototype.get = function(name) {
return this.vertexes.filter(function(el) {
return el.name === name.toString();
})[0]; };
Graph.prototype.edge = function(a, b, w) {
var that = this;
connect(a, b, w);
if (!this.directed) {
connect(b, a, w);
}
function connect(a, b, data) {
var u = that.vertexes.filter(function(el) {
return el.name === a.toString();
})[0];
var v = that.vertexes.filter(function(el) {
return el.name === b.toString();
})[0];
u.adjacent.push(v);
that.edges.push({
from: u,
to: v,
data: data
});
}
return this; };
function main() {
var g = new Graph();
g.vertex(1)
.vertex(2)
.vertex(3)
.vertex(4)
.vertex(5)
.vertex(6)
.vertex(7)
.vertex(8);
g.edge(1, 2, -2);
g.edge(1, 5, -2);
g.edge(1, 6, -3);
g.edge(1, 8, -1);
g.edge(2, 6, 7);
g.edge(2, 8, 4);
g.edge(3, 2, 2);
g.edge(3, 4, 5);
g.edge(3, 7, 9);
g.edge(4, 7, 4);
g.edge(5, 7, 5);
g.edge(7, 8, -1);
g.edge(8, 2, 2);
g.edge(8, 5, 8);
g.edge(8, 6, 3);
g.edge(8, 7, 7);
shortestPath(g, g.get(3));
console.log(g); }
main();
(Shortest path Bellman-Ford)
and don't really get it why it throws the error property 'length' of undefined in the console.
Any advice how to fix this error?

In general, when JS complains Cannot read property "xxx" of undefined, that means that somewhere you have foo.xxx and foo is the JavaScript value undefined (which is not an object, and has no properties).
Track such a problem down by finding the line in question (using debugging tools, or even just looking for .length in your case) and considering: when might the variable in question be undefined?
In your specific case, the error occurs on this line:
for (var i = 0; i < result[0].length; i++) {
which means that result[0] is undefined. Which means that your result array has no value at [0]. It is empty.
Since the printResult function is called from one place (line 59), this likely means that result is still an empty array when printResult() is called. You can confirm this by setting a breakpoint at that location and examining what result is.
As for why it is empty:
The only code that affects the result array is result.push(a) in the printGraph() function. And this function is never called. Ask your friend why s/he defined printGraph() but never invoked it.
It may be as simple as calling printGraph(g) right before printResult().

How to make a function that contains a promise return a value instead of a promise?

Say, I have a function F1 that will be called in many other function. F1 is meant to return a value VAL that will be used in F2. A promise is needed to retrieve that needed data that will help calculate VAL. Having F1 as a promise would cause a lot of confusion in F2, for F1 is often called inside IF statements and FOR loops. Let me illustrate this scenario:
function F1(param1, param2) {
var VAL = 0;
promise(param1, param2).then(function(data) {
for (var i = 0; i < data.length; i++) {
// Do some calculation here
}
});
return VAL;
}
function F2(x1, x2) {
var myArray = [],
someValue = 0;
if ([conditional expression]) {
someValue = F1(x1, x2);
call_some_function();
myArray.push({
val: someValue,
...
});
}
var x = someValue + y;
myArray.push({
id: x,
...
});
return myArray;
}
How do I make sure that F1 returns VAL (integer) so I can use it as a synchronous function?
Thanks in advance for your help.
EDIT:
Here is how the code looks like:
function myFunc(x, y) {
return init()
.then(function() {
return getData(x, y).then(function(data) {
if (data.length == 0) return [];
var id, name,
firstPass = true,
headIn = 0,
headOut = 0,
currentHead = 0,
payWtIn = 0,
payWtOut = 0,
expectedAdg = 0,
weight = 0,
results = [];
for (var i = 0; i < data.length; i++) {
if (firstPass) {
id = data[i].id();
name = data[i].name();
headIn = data[i].headIn();
headOut = data[i].headOut();
expectedAdg = data[i].expectedAdg();
firstPass = false;
}
if (id != data[i].id()) {
buildFunc();
reset();
}
headIn += data[i].headIn();
headOut += data[i].headOut();
payWtIn += data[i].payWtIn();
payWtOut += data[i].payWtOut();
}
buildFunc();
return results;
function buildFunc() {
currentHead = headIn - headOut;
var headDays = getHeadDays({ locationId: locationId, groupId: groupId, callDate: null });
var totalWeight = headIn != 0
? ((((headDays * expectedAdg) + payWtIn) / headIn) * currentHead) + payWtOut
: 0;
results.push({
id: id,
name: name,
headIn: headIn,
headOut: headOut,
headDays: headDays,
currentHd: currentHead,
totalWt: totalWeight
});
}
function reset() {
id = data[i].id();
name = data[i].name();
headIn = data[i].headIn();
headOut = data[i].headOut();
expectedAdg = data[i].expectedAdg();
payWtIn = 0;
payWtOut = 0;
weight = 0;
}
});
});
}
function getHeadDays(params) {
var VAL = 0;
promise(params.a, params.b).then(function(data) {
for (var i = 0; i < data.length; i++) {
// Make calculation to determine VAL here
}
});
return VAL;
}
The init function loads needed entities in the cache (I'm working with BreezeJs) for querying. The getData function gets raw data that are sorted by id from database, and those data are used to determine the results array. As the data are looped through, as long as the id of each record is the same, headIn, headOut, payWtIn and payWtOut are incremented by the record fields, and when the previous and current id are different, we can calculate totalWeight and push a new record to the results array with the buildFunc function. Inside that buildFunc function, we retrieve the headDays in order to calculate totalWeight. The getHeadDays function will be called in many other functions. Please, let me know if you have any questions. Thanks in advance for your help.

You can't.
If you need to return a promise, then that is because the value won't be available until some event happens, and the function will (or at least may) return before then. That's the point of promises.

Javascript - Checking if a number is closer to 2 variables

I have 12 different numbers stored in variables, like this:
var span1 = 8.333333333;
var span2 = 16.66666667;
var span3 = 25;
var span4 = 33.33333333;
var span5 = 41.66666667;
var span6 = 50;
var span7 = 58.33333333;
var span8 = 66.66666667;
var span9 = 75;
var span10 = 83.33333333;
var span11 = 91.66666667;
var span12 = 100;
I have a function which compares a div's width to its parent's width and returns a value as a percentage (minus the % sign), for example, 48.5586. I'd like the function to check which of these span variables the result is closest to. For example, 48.5586 would return "span6" as it's closer to 50 than 41.666667.
Don't really know where to start with this one, any ideas?

Since each span is 8 1/3 % more than the previous one, which is just 100/12, you should be able to use a formula to work out which span class you need.
I worked out the following:
function spanClass(percentWidth) {
return 'span' + Math.round(percentWidth / (100/12));
}
This gives span6 for 48.5586.

The smallest difference can be found by taking the minimum of the absolute value of the difference between your input number and each variable's value.
That said, you should really use a proper data structure, like an object or an array, for mapping these strings to numbers.

Put the values in an array, then you can sort the array on the differece between the values. The smallest differece is first in the array, so that is the closest value:
var spans = [
{ span: 1, value: 8.333333333 },
{ span: 2, value: 16.66666667 },
{ span: 3, value: 25 },
{ span: 4, value: 33.33333333 },
{ span: 5, value: 41.66666667 },
{ span: 6, value: 50 },
{ span: 7, value: 58.33333333 },
{ span: 8, value: 66.66666667 },
{ span: 9, value: 75 },
{ span: 10, value: 83.33333333 },
{ span: 11, value: 91.66666667 },
{ span: 12, value: 100 }
];
var value = 48.5586;
spans.sort(function(x, y){
var a = Math.abs(value - x.value);
var b = Math.abs(value - y.value);
return a == b ? 0 : a < b ? -1 : 1;
});
alert(spans[0].span);
Demo: http://jsfiddle.net/Guffa/77Rf9/

Its better to have array. in my code also i am converting your variables to array and then processing. Eval is bad and should not be used
http://codebins.com/bin/4ldqp6b
var span1 = 8.333333333;
var span2 = 16.66666667;
var span3 = 25;
var span4 = 33.33333333;
var span5 = 41.66666667;
var span6 = 50;
var span7 = 58.33333333;
var span8 = 66.66666667;
var span9 = 75;
var span10 = 83.33333333;
var span11 = 91.66666667;
var span12 = 100;
var arr = [];
for (var i = 0; i < 12; i++) {
eval('arr[' + i + '] = span' + (i + 1));
}
function closestTo(arr, val) {
var closest = 10000,
ind = -1,
diff = 10000; // some random number
for (var i = 0; i < arr.length; i++) {
var tmp = Math.abs(val - arr[i]);
if (diff > tmp) {
diff = tmp;
closest = arr[i];
ind = i;
}
}
alert("Closesnt Number: " + closest + "\nClosest Index:" + ind + "\nclosest variable: span" + (ind + 1))
}
closestTo(arr, 50.12)

Implementation of a closest function in JavaScript. Moved all the spans into an object to make iterating over them easier. Just enumerate all the spans and keep the closest one.
var spans = {
span1: 8.333333333,
span2: 16.66666667,
span3: 25,
span4: 33.33333333,
span5: 41.66666667,
span6: 50,
span7: 58.33333333,
span8: 66.66666667,
span9: 75,
span10: 83.33333333,
span11: 91.66666667,
span12: 100
};
function closest(value) {
var delta
, lastMatch;
Object.keys(spans).forEach(function (span) {
var thisDelta;
if (!delta) {
lastMatch = span;
delta = Math.abs(value - spans[span]);
} else {
thisDelta = Math.abs(value - spans[span]);
if (thisDelta < delta) {
lastMatch = span;
delta = thisDelta;
}
}
});
return lastMatch;
}
var result = closest(48.5586);
console.log(result);
Here a working Codepen example.