How to Truncate Numbers to Two Decimal Places in JavaScript Without Rounding?

Truncating Numbers to Two Decimal Places without Rounding

In JavaScript, the toFixed() method is commonly used to round numerical values to a specified number of decimal places. However, it's possible to truncate values without rounding, ensuring they're displayed with a specific precision.

Consider the value 15.7784514. Using toFixed(), we can easily truncate it to:

num.toFixed(1); // 15.8
num.toFixed(2); // 15.78
num.toFixed(3); // 15.778
num.toFixed(10); // 15.7784514000

However, to truncate the value to 15.77, we need to convert it to a string and use a regular expression to match and capture the numbers up to the second decimal place:

function calc(theform) {
  var num = theform.original.value, rounded = theform.rounded;
  var with2Decimals = num.toString().match(/^-?\d+(?:\.\d{0,2})?/)[0];
  rounded.value = with2Decimals;
}

In this example:

• original is the input where the user enters the original number.
• rounded is the readonly input where the truncated number will be displayed.
• The with2Decimals variable uses a regular expression to extract the number with two decimal places.

Simply update the input values as needed, and the truncated number will be automatically displayed in the rounded input. This method allows for precise truncation of numerical values without the need for rounding.

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