How to detect Esc keypress / Cancel Button on prompt window in JavaScript?-CodePudding

Im unable to capture the esc keypress / cancel button press during the prompt window execution in Javascript.

Because of this, if I do esc / cancel on prompt, its incrementing 1st Value in the array. (answers[0] is getting incremented everytym).

  answers: new Array(5).fill(0),
  registerNewAnswer() {
    let userAnswer =  prompt(
      `${this.question}\n${this.options.join("\n")}\n(Write option number)`
    );
    document.onkeydown = function(e) {
        console.log(key);   /* This statement isn't getting executed on any key press.
    Esc key press / Cancel button press should exit the base function (registerNewAnswer) from here */
    }
    typeof userAnswer === "number" &&
      userAnswer <= this.answers.length &&
      this.answers[userAnswer]  ;
    this.displayResult();
    this.displayResult("string");
  },

CodePudding user response：

The document.onkeydown wouldnt work on the prompt. It works when you press key on your HTML page.

Remove the preceding from the prompt. You can detect the escape/cancel as the prompt will return null in userAnswer. The preceding converts the null to zero.

CodePudding user response：

I had removed the number conversion in assigning place, So I can capture the null value. Number conversion is done atlast.

PFB revised code.

let userAnswer = prompt(
  `${this.question}\n${this.options.join("\n")}\n(Write option number)`
);
if (!userAnswer || userAnswer.trim() === "") return; // 1st to capture esc key / cancel button & 2nd to capture single space input.
userAnswer =  userAnswer;
if (isNaN(userAnswer)) return;
typeof userAnswer === "number" &&
  userAnswer < this.options.length &&
  this.answers[userAnswer]  ;
this.displayResult();
this.displayResult("string");