Introduction to Number Precision in JavaScript

Handling number precision in JavaScript can often be a challenging task due to the floating-point arithmetic issues inherent in the language. The number-precision library offers a robust solution for dealing with these problems by providing dozens of useful APIs for precise mathematical operations. In this article, we will explore these APIs along with practical code snippets and examples.

Basic Usage

First, let’s see how to include number-precision in our project:

  
    // Install via npm
    npm install number-precision --save

    // Include in your project
    const NP = require('number-precision');
  

Essential APIs

Addition

  
    NP.plus(0.1, 0.2); // returns 0.3 instead of 0.30000000000000004
  

Subtraction

  
    NP.minus(0.3, 0.1); // returns 0.2 instead of 0.19999999999999998
  

Multiplication

  
    NP.times(0.1, 0.2); // returns 0.02 instead of 0.020000000000000004
  

Division

  
    NP.divide(0.3, 0.1); // returns 3 instead of 2.9999999999999996
  

Rounding

  
    NP.round(1.005, 2); // returns 1.01
  

Modulus

  
    NP.mod(3, 2); // returns 1
  

Additional Utilities

Strip

Remove the insignificant digits of a number:

  
    NP.strip(0.09999999999999998); // returns 0.1
  

Range

Determine if a number is within a specified range:

  
    NP.range(0.1, 0.099, 0.101); // returns true
  

ToFixed

Convert to fixed-point notation:

  
    NP.toFixed(1.3456, 2); // returns '1.35'
  

Real World Application

Let’s create a simple shopping cart application that uses number-precision to handle price calculations accurately.

  
    // Shopping cart item
    class CartItem {
      constructor(name, price, quantity) {
        this.name = name;
        this.price = price;
        this.quantity = quantity;
      }

      getTotalPrice() {
        return NP.times(this.price, this.quantity);
      }
    }

    // Shopping cart
    class ShoppingCart {
      constructor() {
        this.items = [];
      }

      addItem(item) {
        this.items.push(item);
      }

      getTotalAmount() {
        return this.items.reduce((total, item) => NP.plus(total, item.getTotalPrice()), 0);
      }
    }

    // Usage Example
    const cart = new ShoppingCart();
    cart.addItem(new CartItem('Apple', 0.99, 3));
    cart.addItem(new CartItem('Banana', 1.29, 2));

    console.log('Total Amount: $', cart.getTotalAmount()); // Total Amount: $5.55
  

This application ensures that the total calculations are accurate and free from the typical floating-point arithmetic issues.

Conclusion

In this article, we explored the powerful number-precision library that helps in handling precise number calculations in JavaScript. With dozens of useful APIs and utilities, it is an indispensable tool for developers dealing with financial and scientific computations.

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