Minno - conditions

This repo holds the conditions DSL for minnojs. It holds the function that manages calculating conditions for the POJO DSL used throughout Minno.

Signature

result = conditions(condition, ctx);

Argument	Type	Required	Description
condition	`Condition	Agregator`	Yes
ctx	Object	No	The context object from which to pull paths
returns	Boolean		Whether this condition is true or not

Conditions

Conditions are POJO that describe a proposition. You can think of them as equations.

Argument	Type	Required	Description
left	Any	Yes	The left element of the equation
right	Any	Yes	The right element of the equation
operator	`String	Function`	No
debug	Boolean	No	Whether to log this condition to the console

Left and Right

Each MUST have both a left and a right property that corespond to the left and right sides of the equation.

// 'value' === 'value'
conditions({left:'value', right:'value'}); // true

Any string that has either . or [ is considered to be a path to be taken out of the ctx using lodash get.

// ctx.obj.score === 12 
conditions({left:'obj.score', right:12}, {obj:{score:12}}); // true

// ctx.arr[1] === 12
conditions({left:'arr[1]', right:12}, {arr:[1,2]}); // false

Operator

You can choose the method for comparison using the operator parameter:

// 333 > 100
conditions({left:333, right:100, operator: 'gt'}); // true

Following are the possible values for operator

Value	Description
equals	The default value for operator. Deep equals, treats numbers and string type numbers as equal.
exactly	===
gt	>
greaterThan	>
gte	>=
greaterThanEquals	>=
lt	<
lesserThan	<
lte	<=
lesserThanEquals	<=
in	left in right, when right is an array

You can also use a custom operator by setting it to a function:

// start with the same letter
conditions({left:'hello', right:'hi', operator: (left,right) => left[0] === right[0]}, ctx); // true

Debug

Conditions tend to get rather complicated, many time you will want to know what exactly you are comparing. You can add debug:true to any comparison in order to get a log of the comparison (check your console to see the logs). It is not advisable to set this on too many conditions, this will flood your console and render the information useless.

conditions({left:1, right:1, debug:true}, ctx);

Agregators

You can agregate several conditions by wrapping them in Agregator objects. Agregators have the form of an object with a single property. One exception to this rule is the simple array which is always treated as an and agregator.

The following condition will only be true if cond1 and cond2 are both true:

var cond = {and:[cond1, cond2]};

Following is a list of supported aggregators.

Aggregator	Description
and	If all conditions are true
or	If at least one condition is true
nor	If all conditions are false
nand	If at least one condition is false

Following are several examples for how to create aggregations:

// Condition1 && Condition2
compare({and:[Condition1,Condition2]});

// Condition1 && Condition2 && Condition3
compare([Condition1,Condition2,Condition3]);

// Condition1 || Condition2
compare({or:[Condition1,Condition2]});