A SyntaxError in JavaScript arises when there is an error in the syntax of the code. This can be caused by different issues such as the presence of an extra or missing character, the improper use of keywords or operators, or an unclosed string or comment.
This error can happen due to several reasons, including:
- Missing or extra characters: A SyntaxError can occur if there are missing or extra characters in the code, such as missing parentheses or semicolons, or extra brackets or quotes.
- Incorrect use of keywords or operators: If a keyword or operator is used incorrectly, a SyntaxError can occur. For example, trying to use “if” as a variable name will cause a SyntaxError.
- Unclosed string or comment: If a string or comment is not properly closed, a SyntaxError will be thrown.
- Invalid regular expressions: If a regular expression is not valid, a SyntaxError will be thrown.
- Incompatible code: If you are trying to run code that is not compatible with the current version of JavaScript, a SyntaxError may occur.
JavaScript SyntaxError example
Simple example code SyntaxError threw when missing a closing quotation mark (“) in a line of code:
<!DOCTYPE html>
<html>
<body>
<script>
console.log("Hello World);
</script>
</body>
</html>Output:
The window.onerror() function can be used instead to figure out that there is a syntax error.
<script>
window.onerror = function(e) {
console.log("Error: ", e);
};
</script>
<script>
console.log("Hello World);
</script>Creating a SyntaxError
try {
throw new SyntaxError("Hello", "someFile.js", 10);
} catch (e) {
console.error(e instanceof SyntaxError); // true
console.error(e.message); // Hello
console.error(e.name); // SyntaxError
console.error(e.fileName); // someFile.js
console.error(e.lineNumber); // 10
console.error(e.columnNumber); // 0
console.error(e.stack); // @debugger eval code:3:9
}To avoid SyntaxErrors, it’s important to carefully review your code and ensure that all syntax is correct. This may involve checking for missing or extra characters, making sure that keywords and operators are used correctly, and verifying that strings and comments are properly closed.
Additionally, using a code editor with syntax highlighting and automatic error checking can help catch syntax errors before they cause problems.
Do comment if you have any doubts on this Js error topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version