How to Truncate Numbers to Two Decimals Without Rounding in JavaScript?

Preserving Precision: Truncating Numbers to Two Decimals Without Rounding

Often, when working with numbers, it becomes necessary to display them with a specific number of decimal places. However, using the built-in JavaScript function toFixed() may introduce unintended rounding. To address this, we must consider an alternative approach to accurately truncate numbers without rounding.

Solution: Conversion and Precision Control

To achieve this, we convert the number to a string and employ a regular expression to extract the desired number of decimal places.

function truncate(num, decimals) {
    return num.toString().match(RegExp(`^-?\d+(?:\.\d{0,${decimals}})?`))[0];
}

This function takes a number and the desired number of decimals as parameters. It returns a string representing the truncated value.

Example Usage:

const original = 15.7784514;
const truncated = truncate(original, 2);
console.log(truncated); // Output: "15.77"

In this example, the original value is truncated to two decimal places, resulting in "15.77."

Conclusion:

By harnessing string manipulation and regular expressions, we can effectively truncate numbers to a specified number of decimal places without introducing unwanted rounding. This technique ensures precision in displaying values, particularly when dealing with financial or scientific data.

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