Method set_

packages/mobx/src/types/observablearray.ts:359–398

(index: number, newValue: any)

    }

    set_(index: number, newValue: any) {
        const values = this.values_
        if (this.legacyMode_ && index > values.length) {
            // out of bounds
            die(17, index, values.length)
        }
        if (index < values.length) {
            // update at index in range
            checkIfStateModificationsAreAllowed(this.atom_)
            const oldValue = values[index]
            if (hasInterceptors(this)) {
                const change = interceptChange<IArrayWillChange<any>>(this as any, {
                    type: UPDATE,
                    object: this.proxy_ as any, // since "this" is the real array we need to pass its proxy
                    index,
                    newValue
                })
                if (!change) {
                    return
                }
                newValue = change.newValue
            }
            newValue = this.enhancer_(newValue, oldValue)
            const changed = newValue !== oldValue
            if (changed) {
                values[index] = newValue
                this.notifyArrayChildUpdate_(index, newValue, oldValue)
            }
        } else {
            // For out of bound index, we don't create an actual sparse array,
            // but rather fill the holes with undefined (same as setArrayLength_).
            // This could be considered a bug.
            const newItems = new Array(index + 1 - values.length)
            for (let i = 0; i < newItems.length - 1; i++) {
                newItems[i] = undefined
            } // No Array.fill everywhere...
            newItems[newItems.length - 1] = newValue
            this.spliceWithArray_(values.length, 0, newItems)
        }
    }
}

export function createObservableArray<T>(