Lazy class

lazy.js

/**
 * A lazy value that also memoizes exceptions and checks for recursion.
 */
export class Lazy {
    constructor(init) {
        this.state = State.Init
        this.value = init
    }

    // This shouldn't count against the inline quota.
    _init() {
        this.state = State.Invoke
        try {
            this.value = (0, this.value)()
            this.state = State.Return
            return this.value
        } catch (e) {
            this.value = e
            this.state = State.Throw
            throw this.value
        }
    }

    get() {
        switch (this.state) {
        case State.Init:
            return this._init()
        case State.Invoke:
            throw new TypeError("Invalid recursive read of lazy value")
        case State.Return:
            return this.value
        default:
            throw this.value
        }
    }
}