如何在 JavaScript 中連接字串和變數？

String Concatenation with Variables

In JavaScript, concatenating a string with a variable is a common task. Let's explore how to achieve this in response to the question: "So I am trying to make a string out of a string and a passed variable(which is a number).
How do I do that?"

There are multiple approaches available:

• Concatenation with + Operator:

  You can simply use the + operator to concatenate a string and a variable. For example:

  const id = 42;
  const str = "horseThumb_" + id;

  This would result in str being equal to "horseThumb_42".

• Template Literals (ES2015+):

  With template literals introduced in ECMAScript 2015, you can use backticks (`) to embed variables within strings. For example:

  const id = 42;
  const str = `horseThumb_${id}`;

  This also results in str being equal to "horseThumb_42".

• Element Retrieval with Template Literals:

  When concatenating a string with an element ID, you can use template literals to directly retrieve the element. For example:

  const id = 42;
  const element = document.getElementById(`horseThumb_${id}`);

  This would retrieve the element with the ID "horseThumb_42".

  Example Code:

  Using the AddBorder function provided in the question, we can demonstrate the string concatenation with the + operator:

  function AddBorder(id) {
      const className = "hand positionLeft";
      document.getElementById("horseThumb_" + id).className = className;
  }

  This code would correctly assign the className to the element with the ID "horseThumb_".

  Debugging Tips:

  If your code is not working correctly, consider adding some debugging statements, such as:

  console.log("ID number: " + id);
  console.log("Return value of gEBI: " + document.getElementById("horseThumb_" + id));

  This will help you identify whether the issue lies in passing the ID, whether the element exists, or if the code is being executed before the DOM is ready.

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