EN
TypeScript - foreach with index
8 points
In TypeScript it is possible to create foreach with index in following ways.
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let array : Array<string> = ['a', 'b', 'c'];2
3
array.forEach((item: string, index: number): void => {4
console.log(`${index} : ${item}`);5
});Output:
0 : a
1 : b
2 : cRun it online here.
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let array : Array<string> = ['a', 'b', 'c'];2
let index = 0;3
4
for(let entry of array) {5
console.log(`${index++} : ${entry}`);6
}Output:
0 : a
1 : b
2 : cRun it online here.
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class Entry<T> {2
public constructor(public index: number, public item: T) {3
// nothing here...4
}5
}6
7
function mapArray<T>(array: Array<T>): Array<Entry<T>> {8
let result = array.map((item: T, index: number): Entry<T> => {9
return new Entry<T>(index, item);10
});11
12
return result;13
}Example:
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let array : Array<string> = ['a', 'b', 'c'];2
3
for(let {index, item} of mapArray(array)) {4
console.log(`${index} : ${item}`);5
}Output:
0 : a
1 : b
2 : cRun it online here.
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class Entry<T> {2
public constructor(public index: number, public item: T) {3
// nothing here...4
}5
}6
7
function* mapArray<T>(array: Array<T>): IterableIterator<Entry<T>> {8
for(let i = 0; i < array.length; ++i)9
yield new Entry(i, array[i]);10
}Example:
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let array : Array<string> = ['a', 'b', 'c'];2
3
for(let {index, item} of mapArray(array)) {4
console.log(`${index} : ${item}`);5
}Compiling and running:
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$ tsc -t ES6 Script.ts2
$ node Script.jsOutput:
0 : a
1 : b
2 : cRun it online here.
Note: for
yieldkeyword support--downlevelIterationparameter during compilation is necessary.
