Modify a number by a certain distance. - Node.js Number

Node.js examples for Number:Compare

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Description

Modify a number by a certain distance.

Demo Code


/*/* w ww .  j  a  v a2 s. c  o m*/
  Modify a number by a certain distance.
  e.g. modifyNumber(5.89, 10) = 5.89 + 10 * 0.1
  e.g. modifyNumber(58.9, 20) = 58.9 + 20 * 1

  @param {this} The number to modify.
  @param {Number} distance The distance to modify the number by.
  @return {Number} The modified number.
*/
Number.prototype.modifyBy = function(distance) {

  var parts;
  var exponent;
  var factor;
  var result;
  var decimalPlaces;

  // say we have a number: 5.89
  // we first calculate its exponent: 0
  parts = this.toExponential().split('e');
  exponent = Number(parts[1]);

  // next we subtract 1 from the exponent: -1
  exponent = exponent - 1;

  // then we calculate our desired factor: 10^-1 = 0.1
  factor = Math.pow(10, exponent);

  // next we modify the number by the distance
  result = this + distance * factor;

  // finally we make sure not to add rounding errors
  // how many decimal places does the factor (0.1) have?
  decimalPlaces = (factor.toString().split('.')[1] || "").length;

  // round to that many decimal places (e.g. 2)
  return result.round(decimalPlaces);

};

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