Finding the max value of an attribute in an array of objects

Question

I\'m looking for a really quick, clean and efficient way to get the max \"y\" value in the following JSON slice:

[
  {
    \"x\": \"8/11/2009\",
    \"y\": 0         


        

Answer 1

I'd like to explain the terse accepted answer step-by-step:

var objects = [{ x: 3 }, { x: 1 }, { x: 2 }];

// array.map lets you extract an array of attribute values
var xValues = objects.map(function(o) { return o.x; });
// es6
xValues = Array.from(objects, o => o.x);

// function.apply lets you expand an array argument as individual arguments
// So the following is equivalent to Math.max(3, 1, 2)
// The first argument is "this" but since Math.max doesn't need it, null is fine
var xMax = Math.max.apply(null, xValues);
// es6
xMax = Math.max(...xValues);

// Finally, to find the object that has the maximum x value (note that result is array):
var maxXObjects = objects.filter(function(o) { return o.x === xMax; });

// Altogether
xMax = Math.max.apply(null, objects.map(function(o) { return o.x; }));
var maxXObject = objects.filter(function(o) { return o.x === xMax; })[0];
// es6
xMax = Math.max(...Array.from(objects, o => o.x));
maxXObject = objects.find(o => o.x === xMax);


document.write('
objects: ' + JSON.stringify(objects) + '
');
document.write('
xValues: ' + JSON.stringify(xValues) + '
');
document.write('
xMax: ' + JSON.stringify(xMax) + '
');
document.write('
maxXObjects: ' + JSON.stringify(maxXObjects) + '
');
document.write('
maxXObject: ' + JSON.stringify(maxXObject) + '
');

Further information:

• Math.max.apply()
• Array.prototype.map()
• Array.from()
• Function.prototype.apply()
• Array.prototype.filter()
• Array.prototype.find()