How to Get Line Number and Source URL of Caller Function in JavaScript?

Obtaining Line Number and Source URL of Caller Function in JavaScript

Determining the line number and source URL from which a JavaScript method was invoked can be valuable for debugging purposes and tracing the flow of execution. While there isn't a direct built-in method, we can utilize the Error object's stack property to retrieve this information.

Getting Caller Function Line Number

To obtain the line number where the caller function was called, we can parse the stack property of an Error object:

<code class="js">function getErrorObject() {
  try {
    throw Error('');
  } catch (err) {
    return err;
  }
}

var err = getErrorObject();
var caller_line = err.stack.split("\n")[4];
var index = caller_line.indexOf("at ");
var clean = caller_line.slice(index + 2, caller_line.length);
console.log(clean);</code>

In this example, we throw an error to retrieve the Error object, which contains the call stack. We then split the stack by line breaks and select the fourth line (index 3), which usually contains the caller function information. We trim the leading "at " string to extract the line number.

Getting Caller Function Source URL

Unfortunately, there is no straightforward way to obtain the source URL of the caller function from within the function itself. However, we can use a workaround involving console logging:

<code class="js">function logCallerInfo() {
  console.log("%c", "color: white; background: #000; padding:2px; line-height: 1.5em;",
    err.stack.split("\n")[4]);
}

logCallerInfo();</code>

In this example, we use console logging to display the caller function information in a custom style. The fourth line of the stack (index 3) should include the source URL of the caller function. Inspecting the console output will reveal the desired information.

While these methods provide a way to approximate the caller function line number and source URL, it's important to note that they may not be entirely reliable in all situations.

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