为什么我不能在此片段中生成唯一对象数组?
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我有以下代码片段,我希望过滤原始数组(过滤器)并获得唯一的过滤器数组。
我想我尝试了所有可能的方法,它(uniqueFilters数组)仍然是11个成员原始数组。
怎么了?
如何确保将此数组实际过滤为其中的一些独特元素? (他们都来自同一个地方并且是相同的)
更新: - 答案成功解决了js代码中的问题。 - 在实际的应用程序中,我还必须处理打字稿以使用建议的答案。所以也许会帮助别人:
let newUniqueFilters = Array.from(new Map(filters.map(f => [f._id, f] as [string, any])).values());
var filters = [{
"_id": "filter1",
"filterIndex": 1,
"filterLabel": "Blur",
"filterURL": "url(#filter1)",
"filterEffects": [{
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 5
}]
}]
}, {
"_id": "filter2",
"filterIndex": 2,
"filterLabel": "Shadow",
"filterURL": "url(#filter2)",
"filterEffects": [{
"name": "feOffset",
"attributes": [{
"name": "dx",
"value": 20
}, {
"name": "dy",
"value": 20
}, {
"name": "result",
"value": "offOut"
}, {
"name": "in",
"value": "SourceAlpha"
}]
}, {
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 7
}, {
"name": "in",
"value": "offOut"
}, {
"name": "result",
"value": "blurOut"
}]
}, {
"name": "feBlend",
"attributes": [{
"name": "mode",
"value": "normal"
}, {
"name": "in2",
"value": "blurOut"
}, {
"name": "in",
"value": "SourceGraphic"
}]
}]
}, {
"_id": "filter2",
"filterIndex": 2,
"filterLabel": "Shadow",
"filterURL": "url(#filter2)",
"filterEffects": [{
"name": "feOffset",
"attributes": [{
"name": "dx",
"value": 20
}, {
"name": "dy",
"value": 20
}, {
"name": "result",
"value": "offOut"
}, {
"name": "in",
"value": "SourceAlpha"
}]
}, {
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 7
}, {
"name": "in",
"value": "offOut"
}, {
"name": "result",
"value": "blurOut"
}]
}, {
"name": "feBlend",
"attributes": [{
"name": "mode",
"value": "normal"
}, {
"name": "in2",
"value": "blurOut"
}, {
"name": "in",
"value": "SourceGraphic"
}]
}]
}, {
"_id": "filter1",
"filterIndex": 1,
"filterLabel": "Blur",
"filterURL": "url(#filter1)",
"filterEffects": [{
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 5
}]
}]
}, {
"_id": "filter1",
"filterIndex": 1,
"filterLabel": "Blur",
"filterURL": "url(#filter1)",
"filterEffects": [{
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 5
}]
}]
}, {
"_id": "filter1",
"filterIndex": 1,
"filterLabel": "Blur",
"filterURL": "url(#filter1)",
"filterEffects": [{
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 5
}]
}]
}, {
"_id": "filter2",
"filterIndex": 2,
"filterLabel": "Shadow",
"filterURL": "url(#filter2)",
"filterEffects": [{
"name": "feOffset",
"attributes": [{
"name": "dx",
"value": 20
}, {
"name": "dy",
"value": 20
}, {
"name": "result",
"value": "offOut"
}, {
"name": "in",
"value": "SourceAlpha"
}]
}, {
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 7
}, {
"name": "in",
"value": "offOut"
}, {
"name": "result",
"value": "blurOut"
}]
}, {
"name": "feBlend",
"attributes": [{
"name": "mode",
"value": "normal"
}, {
"name": "in2",
"value": "blurOut"
}, {
"name": "in",
"value": "SourceGraphic"
}]
}]
}, {
"_id": "filter1",
"filterIndex": 1,
"filterLabel": "Blur",
"filterURL": "url(#filter1)",
"filterEffects": [{
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 5
}]
}]
}, {
"_id": "filter2",
"filterIndex": 2,
"filterLabel": "Shadow",
"filterURL": "url(#filter2)",
"filterEffects": [{
"name": "feOffset",
"attributes": [{
"name": "dx",
"value": 20
}, {
"name": "dy",
"value": 20
}, {
"name": "result",
"value": "offOut"
}, {
"name": "in",
"value": "SourceAlpha"
}]
}, {
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 7
}, {
"name": "in",
"value": "offOut"
}, {
"name": "result",
"value": "blurOut"
}]
}, {
"name": "feBlend",
"attributes": [{
"name": "mode",
"value": "normal"
}, {
"name": "in2",
"value": "blurOut"
}, {
"name": "in",
"value": "SourceGraphic"
}]
}]
}, {
"_id": "filter1",
"filterIndex": 1,
"filterLabel": "Blur",
"filterURL": "url(#filter1)",
"filterEffects": [{
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 5
}]
}]
}, {
"_id": "filter2",
"filterIndex": 2,
"filterLabel": "Shadow",
"filterURL": "url(#filter2)",
"filterEffects": [{
"name": "feOffset",
"attributes": [{
"name": "dx",
"value": 20
}, {
"name": "dy",
"value": 20
}, {
"name": "result",
"value": "offOut"
}, {
"name": "in",
"value": "SourceAlpha"
}]
}, {
"name": "feGaussianBlur",
"attributes": [{
"name": "stdDeviation",
"value": 7
}, {
"name": "in",
"value": "offOut"
}, {
"name": "result",
"value": "blurOut"
}]
}, {
"name": "feBlend",
"attributes": [{
"name": "mode",
"value": "normal"
}, {
"name": "in2",
"value": "blurOut"
}, {
"name": "in",
"value": "SourceGraphic"
}]
}]
}]
// first method:
var uniqueFilters = [];
for(let i = 0; i < filters.length; i++) {
if(uniqueFilters.indexOf(filters[i]) == -1){
uniqueFilters.push(filters[i])
}
}
console.log("first method")
console.log("original array length:" + filters.length)
console.log("unique array length:" + uniqueFilters.length)
// second method:
//var uniqueFilters = filters.filter(function(elem, index, self) {
// return index == self.indexOf(elem);
//});
//console.log("second method")
//console.log("original array length:" + filters.length)
//console.log("unique array length:" + uniqueFilters.length)
// suggested method 1:
var newUniqueFilters = Array.from(new Map(filters.map(f => [f._id, f])).values());
console.log(newUniqueFilters)
你可以使用Map
:
filters = Array.from(new Map(filters.map(f => [f._id, f])).values());
这假设它足以比较唯一标识过滤器的_id
值。
请注意,比较对象本身(使用indexOf
或类似方法)将永远不会显示重复项,因为所有对象都是不同的引用(副本),即使它们看起来相同。一般情况下,{} === {}
总是假的。
它不起作用,因为过滤器数组中的每个元素都有不同的内存位置,并且对象通过内存位置进行比较。
因此,每当您在uniqueFilters中比较过滤器数组中存在的该对象时,它就不存在,因为每个对象都有不同的内存位置。所以它将推送uniqueFilters中的每个元素。
尝试更改此行
if(uniqueFilters.indexOf(filters [i])== -1){to if(uniqueFilters.indexOf(filters [i])=== -1){
如果不工作,您也可以尝试将特定属性与所有uniqueFilter进行比较
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