Implementing Function present in string

Question

This sounds like preliminary question but I am unable to figure out a work around. I prefer not to use eval(). Below is my code

        var inputValue = 75;        
        var functionName = 'Math.Sin';          
        alert (functionName(inputValue));

My intent is to calculate the Mathematical Value of functionName(inputValue). Both functionName and inputValue are stored in strings (current setup id designed so and I cannot alter that). functionName and inputValue are variables and their content will change based on context.

Can I get a suggestion on how to calculate value?

thefourtheye · Accepted Answer · 2014-03-12 05:36:20Z

5

You can store the actual functions to be called as key-value pairs, in an object, like this

var functions = {
    "Math.Sin"   : Math.sin,
    "Math.CoSine": Math.cos,
    "Math.Tan"   : Math.tan
};

var inputValue = 75;        
var functionName = 'Math.Sin';          
alert (functions[functionName](inputValue));
# -0.38778163540943045

If the inputValue is in degrees, then you can convert that to radians like this

function convertToRadian(degree) {
    return degree * Math.PI / 180.0;
}

inputValue = convertToRadian(inputValue);

edited Mar 12, 2014 at 5:36

answered Mar 12, 2014 at 5:27

thefourtheye

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2 Comments

JMD Over a year ago

Thank you, this really helps! Any chance I can do this without introducing this new array/JSON? This helps but just in case there is an efficient way..

thefourtheye Over a year ago

@user1998463 Its not JSON, its a JavaScript object and this is the best and the most efficient way, compared to other eval based options.

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