Typescript 맵 반복

Typescript 맵 반복

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타이프 스크립트 맵을 반복하려고하는데 오류가 계속 발생하고 사소한 문제에 대한 해결책을 아직 찾을 수 없습니다.

내 코드는 다음과 같습니다.

myMap : Map<string, boolean>;
for(let key of myMap.keys()) {
   console.log(key);
}

그리고 오류가 발생합니다.

'IterableIteratorShim <[string, boolean]>'유형은 배열 유형 또는 문자열 유형이 아닙니다.

전체 스택 추적 :

 Error: Typescript found the following errors:
  /home/project/tmp/broccoli_type_script_compiler-input_base_path-q4GtzHgb.tmp/0/src/app/project/project-data.service.ts (21, 20): Type 'IterableIteratorShim<[string, boolean]>' is not an array type or a string type.
    at BroccoliTypeScriptCompiler._doIncrementalBuild (/home/project/node_modules/angular-cli/lib/broccoli/broccoli-typescript.js:115:19)
    at BroccoliTypeScriptCompiler.build (/home/project/node_modules/angular-cli/lib/broccoli/broccoli-typescript.js:43:10)
    at /home/project/node_modules/broccoli-caching-writer/index.js:152:21
    at lib$rsvp$$internal$$tryCatch (/home/project/node_modules/rsvp/dist/rsvp.js:1036:16)
    at lib$rsvp$$internal$$invokeCallback (/home/project/node_modules/rsvp/dist/rsvp.js:1048:17)
    at lib$rsvp$$internal$$publish (/home/project/node_modules/rsvp/dist/rsvp.js:1019:11)
    at lib$rsvp$asap$$flush (/home/project/node_modules/rsvp/dist/rsvp.js:1198:9)
    at _combinedTickCallback (internal/process/next_tick.js:67:7)
    at process._tickCallback (internal/process/next_tick.js:98:9)

angular-cli beta5 및 typescript 1.8.10을 사용하고 있으며 목표는 es5입니다. 누구든지이 문제가 있었습니까?

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Map.prototype.forEach((value, key, map) => void, thisArg?) : void대신 사용할 수 있습니다.

다음과 같이 사용하십시오.

myMap.forEach((value: boolean, key: string) => {
    console.log(key, value);
});

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Array.from () 메서드를 사용하여 Array로 변환하십시오.

myMap : Map<string, boolean>;
for(let key of Array.from( myMap.keys()) ) {
   console.log(key);
}

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사용 Array.from , Array.prototype.forEach을 () 하고, 기능을 화살표 :

키를 반복 합니다 .

Array.from(myMap.keys()).forEach(key => console.log(key));

값을 반복 합니다 .

Array.from(myMap.values()).forEach(value => console.log(value));

항목을 반복 합니다 .

Array.from(myMap.entries()).forEach(entry => console.log('Key: ' + entry[0] + ' Value: ' + entry[1]));

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This worked for me. TypeScript Version: 2.8.3

for (const [key, value] of Object.entries(myMap)) { 
    console.log(key, value);
}

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Per the TypeScript 2.3 release notes on "New --downlevelIteration":

for..of statements, Array Destructuring, and Spread elements in Array, Call, and New expressions support Symbol.iterator in ES5/E3 if available when using --downlevelIteration

This is not enabled by default! Add "downlevelIteration": true to your tsconfig.json, or pass --downlevelIteration flag to tsc, to get full iterator support.

With this in place, you can write for (let keyval of myMap) {...} and keyval's type will be automatically inferred.

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Why is this turned off by default? According to TypeScript contributor @aluanhaddad,

It is optional because it has a very significant impact on the size of generated code, and potentially on performance, for all uses of iterables (including arrays).

If you can target ES2015 ("target": "es2015" in tsconfig.json or tsc --target ES2015) or later, enabling downlevelIteration is a no-brainer, but if you're targeting ES5/ES3, you might benchmark to ensure iterator support doesn't impact performance (if it does, you might be better off with Array.from conversion or forEach or some other workaround).

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es5

for (let entry of Array.from(map.entries())) {
    let key = entry[0];
    let value = entry[1];
}

es6

for (let [key, value] of map) {
    console.log(key, value);
}

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I'm using latest TS and node (v2.6 and v8.9 respectively) and I can do:

let myMap = new Map<string, boolean>();
myMap.set("a", true);
for (let [k, v] of myMap) {
    console.log(k + "=" + v);
}

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This worked for me.

Object.keys(myMap).map( key => {
    console.log("key: " + key);
    console.log("value: " + myMap[key]);
});

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Just simple explanation to do it from HTML if you have a Map of types (key, array):

I initialize the array this way:

public cityShop: Map<string, Shop[]> = new Map();

And for iterate over it, I create an array from key values: - just use it as an array with : keys = Array.from(this.cityShop.keys());

Then, in HTML, I can use:

*ngFor="let key of keys"

Inside this bucle, I just get the array value with this.cityShop.get(key)

And... done!

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If you don't really like nested functions, you can also iterate over the keys:

myMap : Map<string, boolean>;
for(let key of myMap) {
   if (myMap.hasOwnProperty(key)) {
       console.log(JSON.stringify({key: key, value: myMap[key]}));
   }
}

Note, you have to filter out the non-key iterations with the hasOwnProperty, if you don't do this, you get a warning or an error.

참고URL : https://stackoverflow.com/questions/37699320/iterating-over-typescript-map