openreachtech/hora-skills-ort-core/hoc-classes-constructor

Classes: Constructor

Conventions related to class constructors.

Do not assign default values to parameters

• Do not assign default values to constructor parameters.
• The constructor's whole responsibility is to hold what its parameters receive. Each one is

assigned to the property of the same name, and no value is decided here.

• Deciding a value the caller did not supply belongs to the factory methods, `static create

(...)` first among them. A default the constructor does not apply is applied there.

// NG: assigning a default value to a parameter
constructor ({
  delimiter = ',',
}) {
  this.delimiter = delimiter
}
// OK: no default value
constructor ({
  delimiter,
}) {
  this.delimiter = delimiter
}

Separate what goes up to the base from what this class keeps

Where a constructor hands part of its parameters to the base class and keeps the rest, a blank line divides the two in the parameter list. The reader then sees, without following super(), which of the properties this class is responsible for.

constructor ({
  ErrorCtor,
  maxDocumentDepth,
}) {
  super({
    ErrorCtor,
  })
  this.maxDocumentDepth = maxDocumentDepth
}

• The factory methods repeat the same division, in their own parameter list and in the

new this({ ... }) they assemble. A class states the split in one shape wherever the list appears, so a reader meeting .create() first learns the same thing.

• A call that hands over the whole list carries no division: super({ ErrorCtor })

lists only the base's share, and nothing is separated inside it.

• The JSDoc above it does not repeat the division. A JSDoc block has no blank line to

divide with, and the *-only line that stands in for one is spent between the description and the first tag — see the JSDoc convention. The type literal stays a flat list of the same properties.

• Tests do not repeat it either. A test assembling the constructor's argument is

building a value, not declaring what the class is made of, so the argument object it writes carries no blank line.