How to Dynamically Modify HTML Element Classes with String Concatenation in JavaScript?

Concatenating Strings with Variables: Decoding the Code

In JavaScript, concatenating strings with variables involves fusing a literal string with a variable's value. This allows us to dynamically create strings incorporating variable data.

In the provided code example:

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

The goal is to dynamically modify the class attribute of an HTML element with an identifier specified by the id variable. To accomplish this, we need to concatenate the literal string 'horseThumb_' with the value of id, resulting in a string representing the element's identifier.

Concatentation Approaches:

1. String Concatenation: We can use the operator to concatenate strings. For instance, 'horseThumb_' id will produce a string like 'horseThumb_42' if id is set to 42.
2. Template Literals (ECMAScript 2015 ): Template literals allow embedding expressions in strings using backticks (`). This method provides a cleaner syntax, as seen in: document.getElementById(horseThumb_${id}).className = "hand positionLeft";`

Troubleshooting Points:

• Ensure that the passed variable is correct and has been initialized with an appropriate value.
• Verify whether the target element with the expected ID exists in the DOM.
• Determine if the function is called at the appropriate time, after the DOM has loaded completely.
• Employ debugging techniques such as using console.log() to track variable values and execution flow.

Remember, string concatenation is essential when dynamically modifying HTML elements, creating dynamic strings, or combining user input into larger text sequences. By understanding the various concatenation techniques, you can effectively manipulate strings and data within JavaScript applications.

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