Math Parser //JavaScript Repository

Description

Mathematical expression parser.
Created: 2005.08.20 - Modified 2006.05.05

Code (Download)

//+ Carlos R. L. Rodrigues
//@ http://jsfromhell.com/classes/math-parser [rev. #3]

MathParser = function(){
    var o = this, p = o.operator = {};
    p["+"] = function(n, m){return n + m;}
    p["-"] = function(n, m){return n - m;}
    p["*"] = function(n, m){return n * m;}
    p["/"] = function(m, n){return n / m;}
    p["%"] = function(m, n){return n % m;}
    p["^"] = function(m, n){return Math.pow(n, m);}
    p["~"] = function(m, n){return Math.sqrt(n, m);}
    o.custom = {}, p.f = function(s, n){
        if(Math[s]) return Math[s](n);
        else if(o.custom[s]) return o.custom[s].apply(o, n);
        else throw new Error("Function \"" + s + "\" not defined.");
    }, o.add = function(n, f){this.custom[n] = f;}
}
MathParser.prototype.eval = function(e, ig){
    var v = [], p = [], i, _, a, c = 0, s = 0, x, t = !ig ? e.indexOf("^") : -1, d = null;
    var cp = e, e = e.split(""), n = "0123456789.", o = "+-/*^%~", f = this.operator;
    if(t + 1)
        do{
            for(a = "", _ = t - 1;  _ && o.indexOf(e[_]) < 0; a += e[_], e[_--] = ""); a += "^";
            for(_ = t + 1, i = e.length; _ < i && o.indexOf(e[_]) < 0; a += e[_], e[_++] = "");
            e = e.slice(0, t).concat((this.eval(a, 1) + "").split("")).concat(e.slice(t + 1));
        }
        while(t = cp.indexOf("^", ++t) + 1);
    for(i = 0, l = e.length; i < l; i++){
        if(o.indexOf(e[i]) > -1)
            e[i] == "-" && (s > 1 || d === null) && ++s, !s && d !== null && (p.push(e[i]), s = 2), "+-".indexOf(e[i]) < (d = null) && (c = 1);
        else if(a = n.indexOf(e[i]) + 1 ? e[i++] : ""){
            while(n.indexOf(e[i]) + 1) a += e[i++];
            v.push(d = (s & 1 ? -1 : 1) * a), c && v.push(f[p.pop()](v.pop(), v.pop())) && (c = 0), --i, s = 0;
        }
    }
    for(c = v[0], i = 0, l = p.length; l--; c = f[p[i]](c, v[++i]));
    return c;
}
MathParser.prototype.parse = function(e){
    var p = [], f = [], ag, n, c, a, o = this, v = "0123456789.+-*/^%~(, )";
    for(var x, i = 0, l = e.length; i < l; i++){
        if(v.indexOf(c = e.charAt(i)) < 0){
            for(a = c; v.indexOf(c = e.charAt(++i)) < 0; a += c); f.push((--i, a));
        }
        else if(!(c == "(" && p.push(i)) && c == ")"){
            if(a = e.slice(0, (n = p.pop()) - (x = v.indexOf(e.charAt(n - 1)) < 0 ? y = (c = f.pop()).length : 0)), x)
                for(var j = (ag = e.slice(n, ++i).split(",")).length; j--; ag[j] = o.eval(ag[j]));
            l = (e = a + (x ? o.operator.f(c, ag) : o.eval(e.slice(n, ++i))) + e.slice(i)).length, i -= i - n + c.length;
        }
    }
    return o.eval(e);
}

Example (Example)

<form id="math" action="">
    <fieldset>
    <legend>MathParser</legend>
    <label>Express?o</label><input type="text" name="exp" value="userFunction(1, 1) + 1" /><br /><br />
    <input type="submit" value="MathParser.parse()" />
    </fieldset>
</form>

<script type="text/javascript">
//<![CDATA[

var parser = new MathParser(), f = document.forms.math;

parser.add("userFunction", function(n, m){
    return n + m;
});

addEvent(f, "submit", function(e){
    try{
        alert(parser.parse(f.exp.value));
    }catch(e){
        alert("Error: " + e);
    }
    return false;
});

//]]>
</script>

Help

Constructor

MathParser(void): Generates an instance of MathParser.

Methods

MathParser.parse(expression: String): Number

Parses a set of pre-defined commands to make a mathematical expression.

expression: mathematical expression that will be parsed

MathParser.add(name: String, handler: Function(args): Number): void

Adds a customized function to the parser.

name: name that should be used in the expression to call the user function
handler: function that will receive the arguments, it must return a number

Basic operations

( and ): Precedence operator

+: Addition

-: Subtraction

*: Multiplication

/: Division

^: Power

~: Square Root

%: Division Reminder

Functions

The class has access to all functions defined in the Math object.

abs: Returns the absolute value of a number

acos: Returns the arccosine of a number

asin: Returns the arcsine of a number

atan: Returns the arctangent of a number

ceil: Returns the smallest integer greater than or equal to its numeric argument

cos: Returns the cosine of a number

exp: Returns e (the base of natural logarithms) raised to a power

floor: Returns the greatest integer less than or equal to its numeric argument

log: Returns the natural logarithm of a number

round: Returns a supplied numeric expression rounded to the nearest integer

sin: Returns the sine of a number

tan: Returns the tangent of a number

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