this is basically Object.assign(options, defaultOptions)
utility javascript module to set object literals used as options for functions
Used to setup option objects with default values.
You have a function taking an object with the possible keys minValue (defaulting to 1) and maxValue (defaulting to 5). The default value are {minValue: 1, maxValue: 5}
// the user overwrites minValue, but uses the default value for maxValue
doStuff({
minValue: 2
});
// doStuff should use the following object as options
{
minValue: 2,
maxValue: 5
}
// doStuff could accomplish this with:
function doStuff(options) {
var defualtOpts = {
minValue: 1,
maxValue: 5
};
// opts is an object with the keys info (details about the change) and value (the options to use)
var opts = defaultify(options, defualtOpts);
opts = opts.value;
// shorter, raising error if the user passes illigal options
// var opts = defaultify(options, defualtOpts, true).value;
...
}
You have a function taking a command (string) as one of the object values. But you want abbreviations to be allowed
// user uses abbreviation for test
doCommand({command: "t"});
// doCommand can use a transform function to change this type
function doCommand(options) {
var defualtOpts = {
command: "run"
};
var transform = {
command: function(value) {
// value is the value passed in by the user, in this case "t"
if (value === "r") return "run";
if (value === "t") return "test";
return value;
}
};
var opts = defaultify(options, defualtOpts, transform, true).value;
...
}
Transform functions can also be used to validate user input. In the example above, the transform object can be changed to
var transform = {
command: function(value) {
if (value === "r" || value === "run") return "run";
if (value === "t" || value === "test") return "test";
throw new Error("Invalid command '" + value + "'");
}
};
// calling doCommand with an invalid command text raises an error
try {
doStuff({command: "say hello"});
} catch (e) {
// e.message === "transform failed: Invalid command 'say hello' for command"
}
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