Use Conditions

What are Conditions

Some of pretty-grid's Grid methods accept an optional Condition to limit the GridPoints that that method affects.

A Condition comes in the form of (point, col, row) => boolean. This method returns true or false for wether the GridPoint needs to be affected by the method or not.

For example, if you only want to draw all the even numbered rows of the grid, use the evenRows condition:

grid.every((point) => whiteDot(point.x, point.y));
grid.every((point) => orangeCircle(point.x, point.y), evenRows());

What are Condition Creators

Although a Condition can be directly supplied to the methods supporting conditions, pretty-grid uses a ConditionCreator that returns a Condition function and accepts any number of parameters (closure).

This way, conditions can configured using various parameters of the ConditionCreator while all methods still rely on the same Condition function type.

Existing Condition Creators

all	all the points in the grid (default)
even	even rows and columns
odd	odd rows and columns
evenCols	even columns
oddCols	odd columns
evenRows	event rows
oddRows	odd rows
cols	all columns from start up and including end fe. cols(1, 5)
rows	all rows from start up and including end fe. rows(2, 4)

Writing your own

if you want to write your own conditions, you have two options:

• write a Condition function if you only use the point's x and y values or it's column or row indices to determine the outcome of the condition

const myCondition = (point, col, row) => {
    // return a boolean based on your condition here based on point, col and/or row
}
// pass the condition function to the Grid method, fe. translate
grid.translate(10, 20, myCondition);

note the absence of braces: You should pass the Condition, not the result of it. The condition gets evaluated inside the Grid method

• Write a ConditionCreator that returns a Condition if you want to provide any number of other arguments to base the condition on.

const myConditionCreator = (arg1, arg2) => {
    return (point, col, row) => {
        // return a boolean based on arg1, arg2, point coordinates or col/row indices.
    }
}
// execute the ConditionCreator function, so a condition is returned and pass it to a Grid method, 
// "50" and "true" are pseudo arguments that the condition could be based on
grid.translate(10, 20, myConditionCreator(50, true));

Here the ConditionCreator needs to be executed, provided with each optional parameters (here 50 and true). The Condition returned by the ConditionCreator is then passed to the Grid method