例子:

0.1+0.2 //0.30000000000000004

1.2-1 //0.19999999999999996

1.15*100 //114.99999999999999

1.2/0.2 //5.999999999999999

方式1 

// 两个浮点数求和
function num_add(num1,num2){var r1,r2,m;try{r1 = num1.toString().split('.')[1].length;}catch(e){r1 = 0;}try{r2=num2.toString().split(".")[1].length;}catch(e){r2=0;}m=Math.pow(10,Math.max(r1,r2));return Math.round(num1*m+num2*m)/m;
}// 两个浮点数相减
function num_subtract(num1,num2){var r1,r2,m;try{r1 = num1.toString().split('.')[1].length;}catch(e){r1 = 0;}try{r2=num2.toString().split(".")[1].length;}catch(e){r2=0;}m=Math.pow(10,Math.max(r1,r2));n=(r1>=r2)?r1:r2;return Number((Math.round(num1*m-num2*m)/m).toFixed(n));
}// 两个浮点数相乘
function num_multiply(num1,num2){var m=0,s1=num1.toString(),s2=num2.toString(); try{m+=s1.split(".")[1].length}catch(e){};try{m+=s2.split(".")[1].length}catch(e){};return Number(s1.replace(".",""))*Number(s2.replace(".",""))/Math.pow(10,m);
}// 两个浮点数相除
function num_divide(num1,num2){var t1,t2,r1,r2;try{t1 = num1.toString().split('.')[1].length;}catch(e){t1 = 0;}try{t2=num2.toString().split(".")[1].length;}catch(e){t2=0;}r1=Number(num1.toString().replace(".",""));r2=Number(num2.toString().replace(".",""));return (r1/r2)*Math.pow(10,t2-t1);
}

结果:

num_add(0.1, 0.2);

num_subtract(1.2,1);

num_multiply(1.15, 100);

num_divide(1.2,0.2);

方式2

引入 bignumber.js

npm install bignumber.js

// 加
function num_add(num1, num2) {return Number(math.add(math.bignumber(num1), math.bignumber(num2)));
}// 减
function num_subtract(num1, num2) {return Number(math.subtract(math.bignumber(num1), math.bignumber(num2)));
}// 乘
function num_multiply(num1, num2) {return Number(math.multiply(math.bignumber(num1), math.bignumber(num2)));
}// 除
function num_divide(num1, num2) {return Number(math.divide(math.bignumber(num1), math.bignumber(num2)));
}

 结果:

num_add(0.1, 0.2);

num_subtract(1.2,1);

num_multiply(1.15, 100);

num_divide(1.2,0.2);