@ou-imdt/utils/lib/modules/DecimalModule.js

Utility library for interactive media development

/**
 * precise floating point calculation
 * @export
 * @class Decimal
 */
export default class DecimalModule {
  #value

  constructor(value) {
    this.#value = value;
  }

  get value() {
    return this.#value;
  }

  calc(value, operator) {
    const scale1 = this.#getScale(this.#value);
    const scale2 = this.#getScale(value);
    const power = (operator === '*') ? null : this.#getPower(scale1, scale2);
    const int1 = this.#getRoundInt(this.#value, power);
    const int2 = this.#getRoundInt(value, power);

    switch (operator) {
      case '+': 
        this.#value = (int1 + int2) / power;
        break;
      case '-':
        this.#value = (int1 - int2) / power;
        break;
      case '*': {
        const power = this.#getPower(scale1 + scale2);
        this.#value = this.#getRoundInt(int1, int2) / power;
        break;
      }
      case '/':
        this.#value = int1 / int2;
        break;
      case '%':
        this.#value = (int1 % int2) / power;
        break;
    }
    return this;
  }

  add(value) {
    return this.calc(value, '+');
  }

  minus(value) {
    return this.calc(value, '-');
  }

  multiply(value) {
    return this.calc(value, '*');
  }

  divide(value) {
    return this.calc(value, '/');
  }

  remainder(value) {
    return this.calc(value, '%');
  }

  round() {
    this.#value = Math.round(this.#value);
    // return this.calc(this.#value, ~);
    return this;
  }

  #getScale(value) {
    const [str, exponent = '0'] = `${value}`.split('e');
    const decimal = `${str}`.split('.')[1] ?? '';
    return decimal.length - Number(exponent);
  }

  #getPower(...args) {
    const exponent = (args.length === 1) ? args[0] : Math.max(...args);
    return Math.pow(10, exponent);
  }

  #getRoundInt(value, power) {
    power = power ?? this.#getPower(this.#getScale(value));
    return Math.round(value * power);
  }
}