Question 409787 in Javascript Question posted in
A very good W3school tutorial can be found here.

Can you reference a variable dynamically using JavaScript for Playwright

I have a JSON file that I’m reading data from for a Playwright test as below:

async answerMyDetails(){
    const testDataFile = './myJsonFile.json'
    let data = await fs.readFile(testDataFile)
    let testData = await JSON.parse(data)

    await this.page.locator(`div:has(> label:has-text("Some Text")) input`).fill(`${testData.myDetailsPageQuestions.vehicleReg.answer_fullUkLicence_carInsurance}`)
}

I’d like to change this so that the _fullUkLicence_carInsurance part of the property that’s being read from the JSON file is not hard coded and can be determined at the time the function is called, e.g. something like:

(answerSet == fullUkLicence_carInsurance)

async answerMyDetails(answerSet){
    const testDataFile = './myJsonFile.json'
    let data = await fs.readFile(testDataFile)
    let testData = await JSON.parse(data)

    await this.page.locator(`div:has(> label:has-text("Some Text")) input`).fill(`${testData.myDetailsPageQuestions.vehicleReg.answer_{answerSet}}`)
}
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2

Answers


  1. 0

    To make the property you’re accessing from the JSON file dynamic, you can use bracket notation in JavaScript. This lets you access an object’s properties based on a variable rather than hard-coding the property key. Here’s how you can update your function:

    async answerMyDetails(answerSet){
    const testDataFile = './myJsonFile.json';
    let data = await fs.readFile(testDataFile);
    let testData = await JSON.parse(data);

    // Use bracket notation to dynamically access the property
    await this.page.locator(`div:has(> label:has-text("Some Text")) input`).fill(`${testData.myDetailsPageQuestions.vehicleReg.answer[answerSet]}`);}

    And here is the explanation on what’s going on here:

    By using answer[answerSet], you can pass the key you want (fullUkLicence_carInsurance, for example) as a parameter when you call the function. This avoids hard-coding the property name and makes it more flexible.

    So, when you call answerMyDetails(‘fullUkLicence_carInsurance’), it will dynamically fill the input field with the corresponding value from your JSON file.

    Hope this helps! Let me know if you have any questions.

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  2. 0

    You can use bracket notation instead of dot notation to dynamically reference an object property name.

    async answerMyDetails(answerSet){
    const testDataFile = './myJsonFile.json'
    let data = await fs.readFile(testDataFile)
    let testData = await JSON.parse(data)

    await this.page.locator(`div:has(> label:has-text("Some Text")) input`)
      .fill(testData.myDetailsPageQuestions.vehicleReg[`answer_${answerSet}`])
}
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