问题:

I'm making a calculator. And the challenge is not to use eval(). I made an array from all the inputs that looks like this:

numbers = [1,1,'+',2,'*',3,'-','(',4,'*',5,'+',2,'/',5,')'];

Then i convert this array to a string, remove the , and i get a string like this:

numberString = "11+2*3-(4*5+2/5)";

So my question is, what is the way to correctly calculate the result of this equation without using eval()?

回答1:

Use an object to map operator strings to functions that implement the operator.

var operators = {
    '+': function(x, y) { return x + y; },
    '-': function(x, y) { return x - y; },
    '*': function(x, y) { return x * y; },
    '/': function(x, y) { return x / y; }
};

The ( function should push the state onto a stack, and ) should pop the stack.

回答2:

Use this,

function notEval(fn) {
  return new Function('return ' + fn)();
}
numbers = [1, 1, '+', 2, '*', 3, '-', '(', 4, '*' , 5, '+', 2,' /', 5, ')'];
console.log( numbers.join('') + ' = ' +  notEval(numbers.join('')) );

Courtesy.