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print out big number in javascript (length > 22)
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| /** | |
| * var big1 = new BigNum('234234234234234'); | |
| * var big2 = new BigNum('234234234234234'); | |
| * big1.multiplyBy(big2).toString(); // will output "54865676487297999188377566756" instead of 5.4865676487298e+28 | |
| */ | |
| var BigNum = function(num) { | |
| if (typeof num === 'string') { | |
| this.parts = []; | |
| while (num.length) { | |
| this.parts.push(parseInt(num.slice(-5),10)); | |
| num = num.substring(0,num.length-5) | |
| } | |
| } else { | |
| this.parts = num; | |
| } | |
| } | |
| BigNum.prototype.multiplyBy = function(bigNum) { | |
| var newParts = []; | |
| for (var i = 0, l1 = this.parts.length; i < l1; ++i) { | |
| for (var j = 0, l2 = bigNum.parts.length; j < l2; ++j) { | |
| var newPartIndex = i + j; | |
| newParts[newPartIndex] = this.parts[i] * bigNum.parts[j] + (newParts[newPartIndex] || 0); | |
| } | |
| } | |
| this._fixOverflows(newParts); | |
| return new BigNum(newParts); | |
| }; | |
| BigNum.prototype.add = function(bigNum) { | |
| var newParts = []; | |
| var length = Math.max(this.parts.length, bigNum.parts.length); | |
| for (var i = 0; i < length; ++i) { | |
| newParts[i] = (this.parts[i] || 0) + (bigNum.parts[i] || 0); | |
| } | |
| this._fixOverflows(newParts); | |
| return new BigNum(newParts); | |
| } | |
| BigNum.prototype._fixOverflows = function(parts) { | |
| for (var k = 0; k < parts.length; ++k) { | |
| var currentPart = parts[k].toString(); | |
| if (currentPart.length > 5) { | |
| var overflowLength = currentPart.length - 5; | |
| var overflow = parseInt(currentPart.substr(0, overflowLength), 10); | |
| parts[k] = parseInt(currentPart.substr(overflowLength), 10) | |
| parts[k + 1] = overflow + (parts[k + 1] || 0); | |
| } | |
| } | |
| } | |
| BigNum.prototype.toString = function() { | |
| var fullNumber = this.parts.map(function(num) { | |
| num = num.toString(); | |
| paddingAmount = 5 - num.length; | |
| for (var i = 0; i < paddingAmount; ++i) { | |
| num = '0' + num; | |
| } | |
| return num | |
| }).reverse().join(''); | |
| while( fullNumber.charAt(0) === '0' && fullNumber.length !== 1) { | |
| fullNumber = fullNumber.substring(1); | |
| } | |
| return fullNumber; | |
| }; | |
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