我想在 JavaScript 中创建一个字典，如下所示：
myMappings = [
{ "Name": 10%},
{ "Phone": 10%},
{ "Address": 50%},
{ "Zip": 10%},
{ "Comments": 20%}
]
我想稍后填充一个 HTML 表格，并将表格的标题设置为 myMappings 的第一列，将列的宽度设置为第二列。有干净的方法吗？
【问题讨论】：
标签： javascript dictionary
另一种方法是创建一个对象数组，每个单独的对象都保存一列的属性。这略微改变了“myMappings”的结构，但更易于使用：
var myMappings = [
{ title: "Name", width: "10%" },
{ title: "Phone", width: "10%" },
{ title: "Address", width: "50%" },
{ title: "Zip", width: "10%" },
{ title: "Comments", width: "20%" }
];
然后您可以使用 for 循环轻松遍历所有“列”：
for (var i = 0; i < myMappings.length; i += 1) {
// myMappings[i].title ...
// myMappings[i].width ...
}
【讨论】：
我看到你所拥有的主要问题是很难循环遍历以填充表格。
只需使用数组数组：
var myMappings = [
["Name", "10%"], // Note the quotes around "10%"
["Phone", "10%"],
// etc..
];
...简化访问：
myMappings[0][0]; // column name
myMappings[0][1]; // column width
或者：
var myMappings = {
names: ["Name", "Phone", etc...],
widths: ["10%", "10%", etc...]
};
并通过以下方式访问：
myMappings.names[0];
myMappings.widths[0];
【讨论】：
[{'Phone':'10%','Name':'10%'},{},{}]。如果您使用的是数组，则您专门使用了某个“顺序”，在这种情况下这无关紧要。
您可能正在尝试使用 JSON 对象：
var myMappings = { "name": "10%", "phone": "10%", "address": "50%", etc.. }
访问：
myMappings.name;
myMappings.phone;
etc..
【讨论】：
从技术上讲，对象就是字典。
var myMappings = {
mykey1: 'myValue',
mykey2: 'myValue'
};
var myVal = myMappings['myKey1'];
alert(myVal); // myValue
你甚至可以循环一个。
for(var key in myMappings) {
var myVal = myMappings[key];
alert(myVal);
}
没有任何理由重新发明轮子。当然，分配是这样的：
myMappings['mykey3'] = 'my value';
And ContainsKey：
if (myMappings.hasOwnProperty('myKey3')) {
alert('key already exists!');
}
我建议你关注这个：http://javascriptissexy.com/how-to-learn-javascript-properly/
【讨论】：
试试：
var myMappings = {
"Name": "10%",
"Phone": "10%",
"Address": "50%",
"Zip": "10%",
"Comments": "20%"
}
// Access is like this
myMappings["Name"] // Returns "10%"
myMappings.Name // The same thing as above
// To loop through...
for(var title in myMappings) {
// Do whatever with myMappings[title]
}
【讨论】：
myMappings.Name 访问。
Object.value 实际上比 Object['value'] 更受欢迎
我建议不要使用数组，除非您需要考虑多个对象。这句话没有错：
var myMappings = {
"Name": 0.1,
"Phone": 0.1,
"Address": 0.5,
"Zip": 0.1,
"Comments": 0.2
};
for (var col in myMappings) {
alert((myMappings[col] * 100) + "%");
}
【讨论】：
在 JavaScript 中模拟 dict 比哈希表更简单、原生且更有效的方法：
它还利用了 JavaScript 是弱类型的。而是类型推断。
方法如下（摘自 Google Chrome 控制台）：
var myDict = {};
myDict.one = 1;
1
myDict.two = 2;
2
if (myDict.hasOwnProperty('three'))
{
console.log(myDict.two);
}
else
{
console.log('Key does not exist!');
}
Key does not exist! VM361:8
if (myDict.hasOwnProperty('two'))
{
console.log(myDict.two);
}
else
{
console.log('Key does not exist!');
}
2 VM362:4
Object.keys(myDict);
["one", "two"]
delete(myDict.two);
true
myDict.hasOwnProperty('two');
false
myDict.two
undefined
myDict.one
1
【讨论】：
这是一个字典，只要 toString() 属性返回唯一值，它就会接受任何类型的键。字典使用任何东西作为键值对的值。
见Would JavaScript Benefit from a Dictionary Object。
按原样使用字典：
var dictFact = new Dict();
var myDict = dictFact.New();
myDict.addOrUpdate("key1", "Value1");
myDict.addOrUpdate("key2", "Value2");
myDict.addOrUpdate("keyN", "ValueN");
字典代码如下：
/*
* Dictionary Factory Object
* Holds common object functions. similar to V-Table
* this.New() used to create new dictionary objects
* Uses Object.defineProperties so won't work on older browsers.
* Browser Compatibility (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties)
* Firefox (Gecko) 4.0 (2), Chrome 5, Internet Explorer 9, Opera 11.60, Safari 5
*/
function Dict() {
/*
* Create a new Dictionary
*/
this.New = function () {
return new dict();
};
/*
* Return argument f if it is a function otherwise return undefined
*/
function ensureF(f) {
if (isFunct(f)) {
return f;
}
}
function isFunct(f) {
return (typeof f == "function");
}
/*
* Add a "_" as first character just to be sure valid property name
*/
function makeKey(k) {
return "_" + k;
};
/*
* Key Value Pair object - held in array
*/
function newkvp(key, value) {
return {
key: key,
value: value,
toString: function () { return this.key; },
valueOf: function () { return this.key; }
};
};
/*
* Return the current set of keys.
*/
function keys(a) {
// remove the leading "-" character from the keys
return a.map(function (e) { return e.key.substr(1); });
// Alternative: Requires Opera 12 vs. 11.60
// -- Must pass the internal object instead of the array
// -- Still need to remove the leading "-" to return user key values
// Object.keys(o).map(function (e) { return e.key.substr(1); });
};
/*
* Return the current set of values.
*/
function values(a) {
return a.map(function(e) { return e.value; } );
};
/*
* Return the current set of key value pairs.
*/
function kvPs(a) {
// Remove the leading "-" character from the keys
return a.map(function (e) { return newkvp(e.key.substr(1), e.value); });
}
/*
* Returns true if key exists in the dictionary.
* k - Key to check (with the leading "_" character)
*/
function exists(k, o) {
return o.hasOwnProperty(k);
}
/*
* Array Map implementation
*/
function map(a, f) {
if (!isFunct(f)) { return; }
return a.map(function (e, i) { return f(e.value, i); });
}
/*
* Array Every implementation
*/
function every(a, f) {
if (!isFunct(f)) { return; }
return a.every(function (e, i) { return f(e.value, i) });
}
/*
* Returns subset of "values" where function "f" returns true for the "value"
*/
function filter(a, f) {
if (!isFunct(f)) {return; }
var ret = a.filter(function (e, i) { return f(e.value, i); });
// if anything returned by array.filter, then get the "values" from the key value pairs
if (ret && ret.length > 0) {
ret = values(ret);
}
return ret;
}
/*
* Array Reverse implementation
*/
function reverse(a, o) {
a.reverse();
reindex(a, o, 0);
}
/**
* Randomize array element order in-place.
* Using Fisher-Yates shuffle algorithm.
*/
function shuffle(a, o) {
var j, t;
for (var i = a.length - 1; i > 0; i--) {
j = Math.floor(Math.random() * (i + 1));
t = a[i];
a[i] = a[j];
a[j] = t;
}
reindex(a, o, 0);
return a;
}
/*
* Array Some implementation
*/
function some(a, f) {
if (!isFunct(f)) { return; }
return a.some(function (e, i) { return f(e.value, i) });
}
/*
* Sort the dictionary. Sorts the array and reindexes the object.
* a - dictionary array
* o - dictionary object
* sf - dictionary default sort function (can be undefined)
* f - sort method sort function argument (can be undefined)
*/
function sort(a, o, sf, f) {
var sf1 = f || sf; // sort function method used if not undefined
// if there is a customer sort function, use it
if (isFunct(sf1)) {
a.sort(function (e1, e2) { return sf1(e1.value, e2.value); });
}
else {
// sort by key values
a.sort();
}
// reindex - adds O(n) to perf
reindex(a, o, 0);
// return sorted values (not entire array)
// adds O(n) to perf
return values(a);
};
/*
* forEach iteration of "values"
* uses "for" loop to allow exiting iteration when function returns true
*/
function forEach(a, f) {
if (!isFunct(f)) { return; }
// use for loop to allow exiting early and not iterating all items
for(var i = 0; i < a.length; i++) {
if (f(a[i].value, i)) { break; }
}
};
/*
* forEachR iteration of "values" in reverse order
* uses "for" loop to allow exiting iteration when function returns true
*/
function forEachR(a, f) {
if (!isFunct(f)) { return; }
// use for loop to allow exiting early and not iterating all items
for (var i = a.length - 1; i > -1; i--) {
if (f(a[i].value, i)) { break; }
}
}
/*
* Add a new Key Value Pair, or update the value of an existing key value pair
*/
function add(key, value, a, o, resort, sf) {
var k = makeKey(key);
// Update value if key exists
if (exists(k, o)) {
a[o[k]].value = value;
}
else {
// Add a new Key value Pair
var kvp = newkvp(k, value);
o[kvp.key] = a.length;
a.push(kvp);
}
// resort if requested
if (resort) { sort(a, o, sf); }
};
/*
* Removes an existing key value pair and returns the "value" If the key does not exists, returns undefined
*/
function remove(key, a, o) {
var k = makeKey(key);
// return undefined if the key does not exist
if (!exists(k, o)) { return; }
// get the array index
var i = o[k];
// get the key value pair
var ret = a[i];
// remove the array element
a.splice(i, 1);
// remove the object property
delete o[k];
// reindex the object properties from the remove element to end of the array
reindex(a, o, i);
// return the removed value
return ret.value;
};
/*
* Returns true if key exists in the dictionary.
* k - Key to check (without the leading "_" character)
*/
function keyExists(k, o) {
return exists(makeKey(k), o);
};
/*
* Returns value assocated with "key". Returns undefined if key not found
*/
function item(key, a, o) {
var k = makeKey(key);
if (exists(k, o)) {
return a[o[k]].value;
}
}
/*
* changes index values held by object properties to match the array index location
* Called after sorting or removing
*/
function reindex(a, o, i){
for (var j = i; j < a.length; j++) {
o[a[j].key] = j;
}
}
/*
* The "real dictionary"
*/
function dict() {
var _a = [];
var _o = {};
var _sortF;
Object.defineProperties(this, {
"length": { get: function () { return _a.length; }, enumerable: true },
"keys": { get: function() { return keys(_a); }, enumerable: true },
"values": { get: function() { return values(_a); }, enumerable: true },
"keyValuePairs": { get: function() { return kvPs(_a); }, enumerable: true},
"sortFunction": { get: function() { return _sortF; }, set: function(funct) { _sortF = ensureF(funct); }, enumerable: true }
});
// Array Methods - Only modification to not pass the actual array to the callback function
this.map = function(funct) { return map(_a, funct); };
this.every = function(funct) { return every(_a, funct); };
this.filter = function(funct) { return filter(_a, funct); };
this.reverse = function() { reverse(_a, _o); };
this.shuffle = function () { return shuffle(_a, _o); };
this.some = function(funct) { return some(_a, funct); };
this.sort = function(funct) { return sort(_a, _o, _sortF, funct); };
// Array Methods - Modified aborts when funct returns true.
this.forEach = function (funct) { forEach(_a, funct) };
// forEach in reverse order
this.forEachRev = function (funct) { forEachR(_a, funct) };
// Dictionary Methods
this.addOrUpdate = function(key, value, resort) { return add(key, value, _a, _o, resort, _sortF); };
this.remove = function(key) { return remove(key, _a, _o); };
this.exists = function(key) { return keyExists(key, _o); };
this.item = function(key) { return item(key, _a, _o); };
this.get = function (index) { if (index > -1 && index < _a.length) { return _a[index].value; } } ,
this.clear = function() { _a = []; _o = {}; };
return this;
}
return this;
}
【讨论】：