Question 210217 in Javascript Question posted in
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Javascript – How to provide type definition while pushing the element into array using TypeScript?

I need to avoid the using of ‘any’ as type definition while pushing the element into array. I tried to provide the type but I am getting an error. Here is the sample code

interface answerProps {
    state: string;
    answer: string;
  }

  const results: Array<string> = [];
  !isEmpty(answers) &&
    answers.map((item: any) => results.push(`${item.state} : ${item.answer}`));

As per the above code , I wanted to avoid of using any while mapping the array element.

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2

Answers


  1. 0

    Just use the answerProps interface while mapping the array.

    interface answerProps {
  state: string;
  answer: string;
}

const results: Array<string> = [];
!isEmpty(answers) &&
  answers.map((item: answerProps) => results.push(`${item.state} : ${item.answer}`));
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  2. 0 
    interface answerProps {
  state: string;
  answer: string;
}

const answers: answerProps[]  = []
const results = answers.map(item => `${item.state} : ${item.answer}`);

    note 1
    there are 2 ways of casting a typed array. For my example, I mainly used the 2nd casting method

    • const arr1: Array<string>
    • const arr2: string[]

    note 2
    in your given sample, array.map is not the correct method to use, try using array.forEach instead

    note 3
    array.map when used correctly, allows typescript to automatically identify the resulted type, and is great to avoid manually casting type to variables

    note 4
    (this is purely preferences) rather then guarding against empty array, try to refactor your code so that it will accepts empty array as valid. In the example I have given above, an empty answers will gets mapped to an empty results

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