(function() {
"use strict";
var arr = [{
"name": "schoolname",
"line id": "0",
"time": "4-5",
"minage": "15",
"maxage": "35"
}, {
"name": "studentname1",
"line id": "1",
"class": "A"
}, {
"name": "studentname2",
"line id": "2",
"class": "B"
}],
headers = ["time", "minage", "maxage"];
//add some more...
for (var i = 3, iLen = 2000; i < iLen; i++) {
arr.push({
name: "studentname" + i,
"line id": String(i),
"class": "C"
});
}
function addHeadersOrig(arr, headers) {
//console.time('addHeadersOrig');
for (var i = 1; i < arr.length; i++) //iterate over the data leaving the 1st line
{
for (var j = 0; j < headers.length; j++) //add each header to the data lines
{
arr[i][headers[j]] = arr[0][headers[j]];
}
}
arr.splice(0, 1);
//console.timeEnd('addHeadersOrig');
return arr;
}
function addHeadersDefineProp(arr, headers) {
//console.time('addHeadersDefineProp');
var header = arr.splice(0, 1)[0],
propObj = headers.reduce(function headerReduce(acc, el) {
acc[el] = {
value: header[el],
writable: true,
enumerable: true
};
return acc;
}, {});
for (var i = 0, len = arr.length; i < len; i++) {
Object.defineProperties(arr[i], propObj);
}
//console.timeEnd('addHeadersDefineProp');
return arr;
}
function addHeadersStrReplace(arr, headers) {
//console.time('addHeadersStrReplace');
var header = arr.shift(),
propObj = {};
for (var i = 0; i < headers.length; i++) {
propObj[headers[i]] = header[headers[i]];
}
//stringify the array, replace each '}' with a ',' followed by the the stringified propObj (minus its opening bracket) which brings its own closing bracket to make up for the one we replaced; then parse back to an object
arr = JSON.parse(JSON.stringify(arr).replace(/\}/g, ',' + JSON.stringify(propObj).slice(1)));
//console.timeEnd('addHeadersStrReplace');
return arr;
}
//only runs using lodash, not underscore
function addHeadersLodashMerge(arr, headers) {
//console.time('addHeadersLodashMerge');
var temp = _.pick(arr.shift(), headers);
for (var i = 0; i < arr.length; i++) {
_.merge(arr[i], temp);
}
//console.timeEnd('addHeadersLodashMerge');
return arr;
}
//runs under both lodash and underscore - faster in underscore AFAICT
function addHeadersUnderscoreDefaults(arr, headers) {
//console.time('addHeadersUnderscoreDefaults');
var temp = _.pick(arr.shift(), headers);
arr.forEach(function(e, i, a) {
a[i] = _.defaults(e, temp);
});
//console.timeEnd('addHeadersUnderscoreDefaults');
return arr;
}
function addHeadersNewFunc(arr, headers) {
//console.time('addHeadersNewFunc');
var header = arr.shift(),
funcBody = ['return item;'],
headerPropName,
setProps;
for(var h = headers.length; h--;) {
headerPropName = headers[h];
funcBody.unshift('item["' + headerPropName + '"]="' + header[headerPropName] + '";'); //unshift since loop is reversed and we want props in same add order as other implementations, and we've already added our first line
}
setProps = new Function('item', funcBody.join('')); //warning, this is a form of 'eval()'...
for (var i = arr.length; i--;)
{
setProps(arr[i]);
}
//console.timeEnd('addHeadersNewFunc');
return arr;
}
function addHeadersLazy(arr, headers) {
//console.time('addHeadersLazy');
var lazy = new Lazy(arr, headers),
result = [];
for (var i = 1; i < arr.length; i++) {
result.push(lazy.get(i));
}
//console.timeEnd('addHeadersLazy');
return result;
}
function addHeadersLazyMemo(arr, headers) {
//console.time('addHeadersLazyMemo');
var lazy = new Lazy(arr, headers, true),
result = [];
for (var i = 1; i < arr.length; i++) {
result.push(lazy.get(i));
}
//console.timeEnd('addHeadersLazyMemo');
return result;
}
function Lazy(arr, headers, useMemo) {
var headerValSrc = arr[0],
headerLen = headers.length,
memo = [];
function _get(index) {
for (var j = 0; j < headerLen; j++) {
arr[index][headers[j]] = headerValSrc[headers[j]];
}
return arr[index];
}
function _getMemo(index) {
if (memo[index]) {
return memo[index];
}
for (var j = 0; j < headerLen; j++) {
arr[index][headers[j]] = headerValSrc[headers[j]];
}
return (memo[index] = arr[index]);
}
return {
get: (useMemo ? _getMemo : _get)
};
}
function clone(data) {
return JSON.parse(JSON.stringify(data));
}
function perfTest(name, testFunc) {
name = name ? name : "Test";
var iterations = 1000,
argsSliced = Array.prototype.slice.call(arguments, 2),
args = [],
t0 = 0,
t1,
t2,
t3,
tmin = 1000000,
tmax = 0,
output;
setTimeout(function delayAllowingDocWrite() {
for (var i = 0; i < iterations; i++) {
args = clone(argsSliced);
t1 = performance.now();
testFunc.apply(this, args);
t2 = performance.now();
t3 = t2 - t1;
tmin = t3 < tmin ? t3 : tmin;
tmax = t3 > tmax ? t3 : tmax;
t0 += t3;
}
output = name + " x " + iterations + ": [Avg] " + (t0/iterations).toFixed(4) + "ms, [Min] " + tmin.toFixed(4) + "ms, [Max] " + tmax.toFixed(4) + "ms";
console.log(output);
document.body.innerHTML += (output + "<br />");
}, 10);
return testFunc.apply(this, clone(argsSliced)); //return output of function immed, once, for comparing results
}
document.body.innerHTML += "Items: " + arr.length + "<br />";
console.log("Items: ", arr.length);
//*
var resultOrig = perfTest("addHeadersOrig", addHeadersOrig, arr, headers),
resultDefineProp = perfTest("addHeadersDefineProp", addHeadersDefineProp, arr, headers),
resultStrReplace = perfTest("addHeadersStrReplace", addHeadersStrReplace, arr, headers),
//resultLodashMerge = perfTest("addHeadersLodashMerge", addHeadersLodashMerge, arr, headers), //re-enable if using lodash.min.js
resultUnderscoreDefaults = perfTest("addHeadersUnderscoreDefaults", addHeadersUnderscoreDefaults, arr, headers),
resultLazy = perfTest("addHeadersLazy", addHeadersLazy, arr, headers),
resultLazyMemo = perfTest("addHeadersLazyMemo", addHeadersLazyMemo, arr, headers),
resultNewFunc = perfTest("addHeadersNewFunc", addHeadersNewFunc, arr, headers);
//*/
var resultOrigStr = JSON.stringify(resultOrig),
outputIsConsistent = "Output of functions is all consistent: " + (
resultOrigStr === JSON.stringify(resultDefineProp) &&
resultOrigStr === JSON.stringify(resultStrReplace) &&
//resultOrigStr === JSON.stringify(resultLodashMerge) &&
resultOrigStr === JSON.stringify(resultUnderscoreDefaults) &&
resultOrigStr === JSON.stringify(resultLazy) &&
resultOrigStr === JSON.stringify(resultLazyMemo) &&
resultOrigStr === JSON.stringify(resultNewFunc)
);
document.body.innerHTML += outputIsConsistent + "<br /><em>Testing...</em><br /><br />";
console.log(outputIsConsistent);
if (!window.performance || !window.performance.now) {
document.body.innerHTML += "Your browser does not seem to support performance.now()...";
}
/*
var arr1 = clone(arr),
arr2 = clone(arr),
arr3 = clone(arr),
arr4 = clone(arr),
arr5 = clone(arr),
arr6 = clone(arr);
var resultOrig = addHeadersOrig(arr1, headers),
resultDefineProp = addHeadersDefineProp(arr2, headers),
resultStrReplace = addHeadersStrReplace(arr3, headers),
resultLodash = addHeadersLodash(arr4, headers),
resultLazy = addHeadersLazy(arr5, headers),
resultLazyMemo = addHeadersLazyMemo(arr6, headers);
console.log(resultOrig);
console.log(resultDefineProp);
console.log(resultStrReplace);
console.log(resultLodash);
console.log(resultLazy);
console.log(resultLazyMemo);
//*/
})();
body {
font-size: 0.8em;
font-family: "Arial", sans-serif;
}
<!--script src="//cdnjs.cloudflare.com/ajax/libs/lodash.js/3.10.0/lodash.min.js"></script-->
<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>
<p>Use a browser that supports performance.now().</p>
Выполняет ли это исполнение оригинал? – JcT
@JcT, наивный тест говорят, что оригинал быстрее – Grundy
Любят ясность этого решения, очень читабельны. – JcT