@logoran/formula-parser

Formula Parser   
==========
Library provides a Parser class that evaluates excel and mathematical formulas.

- - -

Install

A recommended way to install Formula Parser is through NPM using the following command:

``sh
$ npm install @logoran/formula-parser --save
`

Node.js:
`js
var FormulaParser = require('@logoran/formula-parser').Parser;
var parser = new FormulaParser();

parser.parse('SUM(1, 6, 7)'); // It returns Object {error: null, result: 14}
`

Browser:
`html


`


Features

It supports:

* Any numbers, negative and positive as float or integer;
Arithmetic operations like +, -, /, , %, ^;
* Logical operations like AND(), OR(), NOT(), XOR();
* Comparison operations like =, >, >=, <, <=, <>;
* All JavaScript Math constants like PI(), E(), LN10(), LN2(), LOG10E(), LOG2E(), SQRT1_2(), SQRT2();
* String operations like & (concatenation eq. parser.parse('-(2&5)'); will return -25);
* All excel formulas defined in formula.js;
* Relative and absolute cell coordinates like A1, $A1, A$1, $A$1;
* Build-in variables like TRUE, FALSE, NULL
* Custom variables;
* Custom functions/formulas;
* Node and Browser environment.

API (methods)

`js
var parser = new formulaParser.Parser();
`

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Parses and evaluates provided expression. It always returns an object with result and error properties. result property
always keep evaluated value. If error occurs error property will be set as:
* #ERROR! General error;
* #DIV/0! Divide by zero error;
* #NAME? Not recognised function name or variable name;
* #N/A Indicates that a value is not available to a formula;
* #NUM! Occurs when formula encounters an invalid number;
* #VALUE! Occurs when one of formula arguments is of the wrong type.

`js
parser.parse('(1 + 5 + (5 * 10)) / 10'); // returns Object {error: null, result: 5.6}
parser.parse('SUM(MY_VAR)'); // returns Object {error: "#NAME?", result: null}
parser.parse('1;;1'); // returns Object {error: "#ERROR!", result: null}
`

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Set predefined variable name which can be visible while parsing formula expression.

`js
parser.setVariable('MY_VARIABLE', 5);
parser.setVariable('fooBar', 10);

parser.parse('(1 + MY_VARIABLE + (5 * fooBar)) / fooBar'); // returns 5.6
`

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Get variable name.

`js
parser.setVariable('fooBar', 10);

parser.getVariable('fooBar'); // returns 10
`

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Set custom function which can be visible while parsing formula expression.

`js
parser.setFunction('ADD_5', function(params) {
return params[0] + 5;
});
parser.setFunction('GET_LETTER', function(params) {
var string = params[0];
var index = params[1] - 1;

return string.charAt(index);
});

parser.parse('SUM(4, ADD_5(1))'); // returns 10
parser.parse('GET_LETTER("Some string", 3)'); // returns m
`

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Get custom function.

`js
parser.setFunction('ADD_5', function(params) {
return params[0] + 5;
});

parser.getFunction('ADD_5')([1]); // returns 6
`

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List of all supported formulas function.

`js
require('@logoran/formula-parser').SUPPORTED_FORMULAS; // An array of formula names
`

API (hooks)

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Fired while retrieving variable. If variable was defined earlier using setVariable you can overwrite it by this hook.

`js
parser.on('callVariable', function(name, done) {
if (name === 'foo') {
done(Math.PI / 2);
}
});

parser.parse('SUM(SIN(foo), COS(foo))'); // returns 1
`

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Fired while calling function. If function was defined earlier using setFunction you can overwrite it's result by this hook.
You can also use this to override result of build-in formulas.

`js
parser.on('callFunction', function(name, params, done) {
if (name === 'ADD_5') {
done(params[0] + 5);
}
});

parser.parse('ADD_5(3)'); // returns 8
`

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Fired while retrieving cell value by its label (eq: B3, B$3, B$3, $B$3).

`js
parser.on('callCellValue', function(cellCoord, done) {
// using label
if (cellCoord.label === 'B$6') {
done('hello');
}
// or using indexes
if (cellCoord.row.index === 5 && cellCoord.row.isAbsolute && cellCoord.column.index === 1 && !cellCoord.column.isAbsolute) {
done('hello');
}

if (cellCoord.label === 'C6') {
done(0.75);
}
});

parser.parse('B$6'); // returns "hello"
parser.parse('B$6&" world"'); // returns "hello world"
parser.parse('FISHER(C6)'); // returns 0.9729550745276566
`

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Fired while retrieving cells range value (eq: A1:B3, $A1:B$3, A$1:B$3, $A$1:$B$3).

`js
parser.on('callRangeValue', function(startCellCoord, endCellCoord, done) {
var data = [
[1, 2, 3, 4, 5],
[6, 7, 8, 9, 10],
[11, 12, 13, 14, 15],
[16, 17, 18, 19, 20],
];
var fragment = [];

for (var row = startCellCoord.row.index; row <= endCellCoord.row.index; row++) {
var rowData = data[row];
var colFragment = [];

for (var col = startCellCoord.column.index; col <= endCellCoord.column.index; col++) {
colFragment.push(rowData[col]);
}
fragment.push(colFragment);
}

if (fragment) {
done(fragment);
}
});

parser.parse('JOIN(A1:E2)'); // returns "1,2,3,4,5,6,7,8,9,10"
parser.parse('COLUMNS(A1:E2)'); // returns 5
parser.parse('ROWS(A1:E2)'); // returns 2
parser.parse('COUNT(A1:E2)'); // returns 10
parser.parse('COUNTIF(A1:E2, ">5")'); // returns 5
``

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Please see CONTRIBUTING.md.

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To see the list of recent changes, see Releases section.

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The MIT License (see the LICENSE file for the full text).