从这个最初的问题,我将如何在多个字段应用排序?
使用这种稍作调整的结构,我将如何排序城市(上升)和价格(下降)?
var homes = [
{"h_id":"3",
"city":"Dallas",
"state":"TX",
"zip":"75201",
"price":"162500"},
{"h_id":"4",
"city":"Bevery Hills",
"state":"CA",
"zip":"90210",
"price":"319250"},
{"h_id":"6",
"city":"Dallas",
"state":"TX",
"zip":"75000",
"price":"556699"},
{"h_id":"5",
"city":"New York",
"state":"NY",
"zip":"00010",
"price":"962500"}
];
我喜欢的事实是,给出的答案提供了一个一般的方法。在我计划使用这段代码的地方,我将不得不对日期以及其他东西进行排序。“启动”对象的能力似乎很方便,如果不是有点麻烦的话。
我试图把这个答案构建成一个很好的通用示例,但我运气不太好。
只需遵循排序标准列表
即使要封装36个排序标准,这段代码也将始终保持可读和可理解
Nina在这里提出的解决方案当然非常优雅,但它意味着要知道在布尔逻辑中,值为0对应的值为false,并且布尔测试在JavaScript中可以返回除true / false以外的值(这里是数值),这对于初学者来说总是令人困惑。
还要考虑谁需要维护您的代码。也许会是你:想象一下你自己花了几天的时间在另一个人的代码上,然后有了一个有害的错误……你读了几千行充满技巧的文章,都累坏了
const homes =
[ { h_id: '3', city: 'Dallas', state: 'TX', zip: '75201', price: '162500' }
, { h_id: '4', city: 'Bevery Hills', state: 'CA', zip: '90210', price: '319250' }
, { h_id: '6', city: 'Dallas', state: 'TX', zip: '75000', price: '556699' }
, { h_id: '5', city: 'New York', state: 'NY', zip: '00010', price: '962500' }
]
const fSort = (a,b) =>
{
let Dx = a.city.localeCompare(b.city) // 1st criteria
if (Dx===0) Dx = Number(b.price) - Number(a.price) // 2nd
// if (Dx===0) Dx = ... // 3rd
// if (Dx===0) Dx = ... // 4th....
return Dx
}
console.log( homes.sort(fSort))
这是另一个可能更接近您对语法的想法的例子
function sortObjects(objArray, properties /*, primers*/) {
var primers = arguments[2] || {}; // primers are optional
properties = properties.map(function(prop) {
if( !(prop instanceof Array) ) {
prop = [prop, 'asc']
}
if( prop[1].toLowerCase() == 'desc' ) {
prop[1] = -1;
} else {
prop[1] = 1;
}
return prop;
});
function valueCmp(x, y) {
return x > y ? 1 : x < y ? -1 : 0;
}
function arrayCmp(a, b) {
var arr1 = [], arr2 = [];
properties.forEach(function(prop) {
var aValue = a[prop[0]],
bValue = b[prop[0]];
if( typeof primers[prop[0]] != 'undefined' ) {
aValue = primers[prop[0]](aValue);
bValue = primers[prop[0]](bValue);
}
arr1.push( prop[1] * valueCmp(aValue, bValue) );
arr2.push( prop[1] * valueCmp(bValue, aValue) );
});
return arr1 < arr2 ? -1 : 1;
}
objArray.sort(function(a, b) {
return arrayCmp(a, b);
});
}
// just for fun use this to reverse the city name when sorting
function demoPrimer(str) {
return str.split('').reverse().join('');
}
// Example
sortObjects(homes, ['city', ['price', 'desc']], {city: demoPrimer});
演示:http://jsfiddle.net/Nq4dk/2/
编辑:只是为了好玩,这里有一个变化,只需要一个类似sql的字符串,所以你可以做sortObjects(房屋,“城市,价格desc”)
function sortObjects(objArray, properties /*, primers*/) {
var primers = arguments[2] || {};
properties = properties.split(/\s*,\s*/).map(function(prop) {
prop = prop.match(/^([^\s]+)(\s*desc)?/i);
if( prop[2] && prop[2].toLowerCase() === 'desc' ) {
return [prop[1] , -1];
} else {
return [prop[1] , 1];
}
});
function valueCmp(x, y) {
return x > y ? 1 : x < y ? -1 : 0;
}
function arrayCmp(a, b) {
var arr1 = [], arr2 = [];
properties.forEach(function(prop) {
var aValue = a[prop[0]],
bValue = b[prop[0]];
if( typeof primers[prop[0]] != 'undefined' ) {
aValue = primers[prop[0]](aValue);
bValue = primers[prop[0]](bValue);
}
arr1.push( prop[1] * valueCmp(aValue, bValue) );
arr2.push( prop[1] * valueCmp(bValue, aValue) );
});
return arr1 < arr2 ? -1 : 1;
}
objArray.sort(function(a, b) {
return arrayCmp(a, b);
});
}
您可以使用lodash或derby函数lodash
它有两个参数字段数组和方向数组('asc','desc')
var homes = [
{"h_id":"3",
"city":"Dallas",
"state":"TX",
"zip":"75201",
"price":"162500"},
{"h_id":"4",
"city":"Bevery Hills",
"state":"CA",
"zip":"90210",
"price":"319250"},
{"h_id":"6",
"city":"Dallas",
"state":"TX",
"zip":"75000",
"price":"556699"},
{"h_id":"5",
"city":"New York",
"state":"NY",
"zip":"00010",
"price":"962500"}
];
var sorted =. data._.orderBy(data, ['city', 'price'], ['asc','desc'])
一种多维排序方法,基于这个答案:
更新:这是一个“优化”版本。它做了更多的预处理,并预先为每个排序选项创建了一个比较函数。它可能需要更多的内存(因为它为每个排序选项存储了一个函数,但它应该更好一点,因为它不必在比较期间确定正确的设置。不过我没有做过任何侧写。
var sort_by;
(function() {
// utility functions
var default_cmp = function(a, b) {
if (a == b) return 0;
return a < b ? -1 : 1;
},
getCmpFunc = function(primer, reverse) {
var dfc = default_cmp, // closer in scope
cmp = default_cmp;
if (primer) {
cmp = function(a, b) {
return dfc(primer(a), primer(b));
};
}
if (reverse) {
return function(a, b) {
return -1 * cmp(a, b);
};
}
return cmp;
};
// actual implementation
sort_by = function() {
var fields = [],
n_fields = arguments.length,
field, name, reverse, cmp;
// preprocess sorting options
for (var i = 0; i < n_fields; i++) {
field = arguments[i];
if (typeof field === 'string') {
name = field;
cmp = default_cmp;
}
else {
name = field.name;
cmp = getCmpFunc(field.primer, field.reverse);
}
fields.push({
name: name,
cmp: cmp
});
}
// final comparison function
return function(A, B) {
var a, b, name, result;
for (var i = 0; i < n_fields; i++) {
result = 0;
field = fields[i];
name = field.name;
result = field.cmp(A[name], B[name]);
if (result !== 0) break;
}
return result;
}
}
}());
使用示例:
homes.sort(sort_by('city', {name:'price', primer: parseInt, reverse: true}));
DEMO
最初的功能:
var sort_by = function() {
var fields = [].slice.call(arguments),
n_fields = fields.length;
return function(A,B) {
var a, b, field, key, primer, reverse, result, i;
for(i = 0; i < n_fields; i++) {
result = 0;
field = fields[i];
key = typeof field === 'string' ? field : field.name;
a = A[key];
b = B[key];
if (typeof field.primer !== 'undefined'){
a = field.primer(a);
b = field.primer(b);
}
reverse = (field.reverse) ? -1 : 1;
if (a<b) result = reverse * -1;
if (a>b) result = reverse * 1;
if(result !== 0) break;
}
return result;
}
};
DEMO
下面是一种可扩展的按多个字段排序的方法。
homes.sort(function(left, right) {
var city_order = left.city.localeCompare(right.city);
var price_order = parseInt(left.price) - parseInt(right.price);
return city_order || -price_order;
});
笔记
A function passed to array sort is expected to return negative, zero, positive to indicate less, equal, greater.
a.localeCompare(b) is universally supported for strings, and returns -1,0,1 if a<b,a==b,a>b.
Subtraction works on numeric fields, because a - b gives -,0,+ if a<b,a==b,a>b.
|| in the last line gives city priority over price.
Negate to reverse order in any field, as in -price_order
Add new fields to the or-chain: return city_order || -price_order || date_order;
Date compare with subtraction, because date math converts to milliseconds since 1970.var date_order = new Date(left.date) - new Date(right.date);
Boolean compare with subtraction, which is guaranteed to turn true and false to 1 and 0 (therefore the subtraction produces -1 or 0 or 1). var goodness_order = Boolean(left.is_good) - Boolean(right.is_good)This is unusual enough that I'd suggest drawing attention with the Boolean constructor, even if they're already boolean.