How to Encode HTML and JavaScript?

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You can encode HTML and JavaScript using functions or libraries that convert special characters into their corresponding HTML entities or escape sequences.

Here’s an example of encoding HTML in JavaScript:

let str = '<h1>Hello, World!</h1>';

str = str.replace(/[&<>"']/g, function(m) {
  return {
    '&': '&',
    '<': '<',
    '>': '>',
    '"': '"',
    "'": '''
  }[m];
});

console.log(str); // Output: '<h1>Hello, World!</h1>'

In this example, the .replace() method is called on the string str. The first parameter to the method is a regular expression that matches the characters &, <, >, ", and '. The second parameter is a function that takes the matched character as its argument and returns the corresponding HTML entity. This function uses an object literal to map characters to entities.

The g flag in the regular expression makes the .replace() method perform a global search, so all occurrences of the characters are replaced.

For JavaScript, you can encode characters that have special meaning in JavaScript by escaping them. For example, you can escape single quotes ' and newline characters \n. Here’s an example:

let str = "Hello, 'world'!";

str = str.replace(/'/g, "\\'");

console.log(str); // Output: "Hello, \\'world\\'!"

In this example, the .replace() method is called on the string str. The first parameter to the method is a regular expression that matches the single quote character '. The second parameter is a string that replaces the matched character with a string that contains two characters: a backslash \ and a single quote '. The backslash is used to escape the single quote, so that it is treated as a literal character and not as the end of the string.

Note that these examples show the manual implementation of encoding. You can also use libraries such as the escape-html package in Node.js to simplify the process.

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