此javascript代码块是什么意思？

Question

I came accross a code block in javascript. Can you please tell me its meaning?

var result = {
    diagmetric : diag * 2.54,
    sizex : xd,
    sizey : yd,
    metricsizex : 2.54*xd,
    metricsizey : 2.54*yd,
    xppi : x/xd,
    yppi : y/yd,
    dotpitch : pitch,
    sqppi : x/xd*y/yd
};

Full function :

function calc_dpi (x,y,diag) {
    if (y == 0 || x == 0) return;
    var ratio = y/x;
    var xd = Math.sqrt( Math.pow(diag,2) / ( 1 + Math.pow(ratio, 2) ));
    var yd = xd * ratio;
    var pitch = 25.4/(x/xd); // metric
    var result = {
        diagmetric : diag * 2.54,
        sizex : xd,
        sizey : yd,
        metricsizex : 2.54*xd,
        metricsizey : 2.54*yd,
        xppi : x/xd,
        yppi : y/yd,
        dotpitch : pitch,
        sqppi : x/xd*y/yd
    };
    return result;
}

Answer 1

Here you asign the Object to the result var. In JS you can define the fields in the object this way:

var obj = {fieldA:A, fieldB:B};

Answer 2

That's a JS Object Literal. Think of it as an associative array.

https://stackoverflow.com/a/3831209/1410212

Answer 3

Syntactically, it's just a literal object assignment. A new object is created by the {...} expression with the specified properties and values. Semantically, it packs the return values of the function in a new plain object and returns the object.

Answer 4

it defines a javascript object using 6 parameters (that are surely defined as function parameters into which the var is defined):

x,y,diag,xd,yd,pitch

i suppose xd & yd are inches size x & y are pixel size diag : i suppose diagonal pitch : some pitch info.

this javascript object stores structured info (as any object) that define

Answer 5

This function calculates the dpi and returns an object with the results. The Object is written in literal notation. It's a common way in javascript to not only return a single value from a function but a full object or even another function.

You can use it the following way:

var result = calc_dpi(/* your parameters*/)
// now you have access to the result by calling the properties
// of the result object e.g. with:
alert(result.dotpitch);