[英]Using dictionary to map against an API response and create array of objects, trying to remove duplicates
我有一个 React 组件,我在其中使用字典来比较地址状态的 API 响应,并仅映射作为下拉列表中的选项返回的状态。
这是我用来创建返回状态数组的映射函数:
let activeStates = props.locations.map(x => ({abbr: x.address.state, name: states[x.address.state]as string}));
对照我的字典,它看起来像这样:
const states = {
AL: "Alabama",
AK: "Alaska",
AZ: "Arizona",
AR: "Arkansas",
CA: "California",
CO: "Colorado",
(all US states are included)
};
这会在响应中创建一个包含所有位置地址的数组,如下所示:
3:
abbr: "3"
name: {abbr: "TN", name: "Tennessee"}
__proto__: Object
4:
abbr: "4"
name: {abbr: "WI", name: "Wisconsin"}
__proto__: Object
5:
abbr: "5"
name: {abbr: "NC", name: "North Carolina"}
__proto__: Object
6:
abbr: "6"
name: {abbr: "NC", name: "North Carolina"}
这为我将数组映射到下拉列表的组件提供了信息:
<select value={state} onChange={handleStateChange}>
<option value={''}>All</option>
{activeStates.map((state) => (
<option value={state.abbr}>{state.name}</option>))}
</select>
我正在尝试编写一个使用activeStates
的函数来创建每个状态/缩写中只有一个的新数组,而不是生成重复项。 我知道因为该映射数组中返回的所有值都被认为是唯一的,所以我需要运行一个索引函数来消除重复项,但我不确定如何。
到目前为止,我已经使用了:
let statesObj = props.locations.reduce((acc, curr) => {
acc[curr.address.state] = states[curr.address.state];
return acc;
}, {});
let uniqueStates = Object.entries(statesObj).map(([abbr, name]) => ({abbr, name }));
let activeStates = props.locations.map(x => ({abbr: x.address.state, name: states[x.address.state]}));
let uniqueStates = new Set(activeStates);
let uniqueStatesArray = [...uniqueStates]
和
let activeStates = Array.from(new Set(props.locations.map(x => ({ abbr: x.address.state, name: states[x.address.state]})))
这些都没有奏效。
你走在正确的轨道上。
将对象添加到 Set 时,它是通过引用:
const s = new Set()
const o = { a: 1, b: 2 }
s.add(o)
console.log(s.has(o)) // true
console.log(s.has({ a: 1, b: 2 })) // false
这可能会导致您可能无法预料的其他影响:
const s = new Set()
s.add({ a: 1, b: 2 })
s.add({ a: 1, b: 2 })
s.add({ a: 1, b: 2 })
console.log(s) // Set { { a: 1, b: 2 }, { a: 1, b: 2 }, { a: 1, b: 2 } }
要回答您的问题,您可以使用对象的属性之一添加到用于检查的集合中:
const dropDuplicates = arr => {
const seen = new Set()
const result = []
for (let obj of arr) {
if (!seen.has(obj.abbr)) { // check if `abbr` has been seen
result.push(obj) // if not, then add state to result
seen.add(obj.abbr) // this state is now seen, don't add anymore
}
}
return result
}
我最终通过将一些映射函数与过滤器链接在一起来解决它,例如:
let activeStates = props.locations.map(x => ({abbr: x.address.state, name: states[x.address.state]as string}));
function getUnique(activeStates, comp) {
const unique = activeStates
.map(e => e[comp])
// store the keys of the unique states
.map((e, i, final) => final.indexOf(e) === i && i)
// eliminate the duplicate keys and store unique states
.filter(e => activeStates[e]).map(e => activeStates[e]);
return unique;
}
let uniqueStates = getUnique(activeStates, 'abbr')
有点迂回,但最终成功了,现在所有选项都正确映射。 谢谢大家的好建议!
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