Handling String Comparison Issues Caused by HTML Encodings and Line Breaks

Overview

During implementation, we encountered an issue where string values were not matching correctly due to inconsistencies in how they were stored and compared. Specifically:

• Some values contained HTML entities like < and > instead of < and >.
• Some values included HTML line breaks (<br>), carriage returns, or multiple spaces.
• As a result, direct string comparisons were failing, even though the actual content was intended to be the same.

To ensure reliable comparisons, we implemented a string normalization function.

Root Cause

1. HTML Encoding: Certain values were stored with encoded symbols (< vs <).
2. Line Break Variations: Line breaks were represented as <br> tags or rn.
3. Whitespace Inconsistencies: Multiple consecutive spaces were sometimes present.

These variations meant that two logically identical strings could appear different to the system.

Solution – Normalization Function

We introduced a normalize() function that cleans and standardizes strings before comparison.

function normalize(str) {
    if (!str || typeof str !== 'string') return '';

    // Decode HTML entities for < and >
    str = str.replace(/&lt;/g, '<').replace(/&gt;/g, '>');

    return str
        // Replace <br> with a space
        .replace(/<brs*/?>/gi, ' ')
        // Replace newlines (r, n) with a space
        .replace(/[rn]+/g, ' ')
        // Collapse multiple spaces into one
        .replace(/s+/g, ' ')
        // Remove leading/trailing whitespace
        .trim();
}

How It Works

1. Decode Entities – Converts < → <, > → >.
2. Unify Line Breaks – Replaces <br> tags and rn with a single space.
3. Standardize Whitespace – Collapses multiple spaces into one.
4. Trim – Removes leading and trailing spaces.

Example

let input1 = "Hello<br>World";
let input2 = "Hello <br> World";

normalize(input1); // "Hello World"
normalize(input2); // "Hello World"

// Safe comparison
if (normalize(input1) === normalize(input2)) {
    console.log("Strings are equal");
}

Result: Both inputs normalize to "Hello World", ensuring consistent comparison.