Convert operator from string type to operator type

问题

I want to generate something like this at random.

233 + 333 = 566

I mean the first number and the operator and the second number are generated at random.

So, I wrote this code now.

var x = parseInt(Math.random()*1000),
    y = parseInt(Math.random()*1000),
    operators = ['+', '-', '*', '/'],
    operatorNum = parseInt(Math.random()*4),
    operator = operators[operatorNum],
    result;

result = x + operator + y;

But this just gives me something like "748/264" as a string. It doesn't give me the result of the calculation generated.

I suppose I need to convert operator from string to operator type. But, I don't think there is a operator type.

Edited

I'm building a Chrome extension. As per the Chrome extension policy, I'm not allowed to use the eval function.

回答1:

Evaluate it:

result = eval(x + operator + y);

EDIT

Since you can't use eval, you need to build your own math functions. You can just specify the four functions inside that array (if you don't actually need to know their names), like:

myFunctions = [
    function(a, b){return a+b;}, 
    function(a, b){return a-b;}, 
    function(a, b){return a/b;}, 
    function(a, b){return a*b;}
];

Then just randomly pick one and call it with your x and y variables as parameters, just like you did before: result = myFunctions[parseInt(Math.random()*4)](x, y);.

回答2:

There are no built-in operator functions in JavaScript, but you can make your own pretty easily:

var operators = {
    '+': function(a, b) {
        return a + b;
    },
    '*': function(a, b) {
        return a * b;
    },
    ....
};

And then call the appropriate operator:

operators['+'](4, 7);  // 11

But here, you can just use eval and treat your string as JavaScript code:

eval('2 + 2');  // 4

回答3:

I think the solution here is to use eval()

result = eval(x + operator + y)

In this case it is safe to use eval, but Be warned - It is a dangerous function to use

来源：https://stackoverflow.com/questions/18679876/convert-operator-from-string-type-to-operator-type

标签

javascript

jquery

google-chrome-extension