Convert equation string to equation

Question

Possible Duplicate:
Running an equation with Javascript from a text field

How can I convert the following:

var n = "2x^3+3x+6";

To

var x = a number
var n = 2x^3+3x+6;

In JavaScript?

You'll have to write a parser for the expression grammar you intend to use. — Pointy, Jan 10 '13 at 16:50
The `^` operator in JavaScript is binary XOR, not the power as you seem to expect. — Bergi, Jan 10 '13 at 16:50
I don't think this is a duplicate at all; the syntax in this question is definitely not JavaScript. — Pointy, Jan 10 '13 at 17:08

score 16 · Accepted Answer · answered Jan 10 '13 at 17:06

Quite hard to guess what the exact requirements and the context are, but if you want to roughly stick to the grammar demonstrated by your variable I'd suggest using a math expression parser.

Using js-Expression-eval, it could look like this:

var formula = "2*x^3+3*x+6";
var expression = Parser.parse(formula);
var result = expression.evaluate({ x: 3 });

Run the Fiddle

Should you want to have your own grammar - to leave out the * symbols for multiplication with variables, for example - you'll have to roll your own parser, for example using something like jison.

great super easy solution, thank you! – Ka Tech Feb 18 '18 at 03:38 — Ka Tech, Feb 18 '18 at 03:38

score 15 · Answer 2 · edited Jan 10 '13 at 17:00

15

var x = a number;
var n = eval("2*Math.pow(x,3)+3*x+6")

edited Jan 10 '13 at 17:00

Shmiddty

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answered Jan 10 '13 at 16:53

Michaël Benjamin Saerens

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Where did you get `Math.pow` from `"2x^3+3x+6"`? – ATOzTOA Jan 10 '13 at 16:55
+1 an excellent answer if only to highlight a poorly-asked question! – PeteH Jan 10 '13 at 16:56
4

@PeteH the question isn't necessarily poorly-asked; perhaps the OP does not want to use JavaScript syntax for his equations. – Pointy Jan 10 '13 at 17:09

Convert equation string to equation

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