This is what I call clean coding

ResumeCreator.js

import assert from 'assert';

updateStepFourProps(type, operation, id) {
    assert(Array.isArray(this.state[type]), `Cannot do operation on type '${type}'`)

    switch (operation) {
        case 'add':
            this.setState({
                [type]: this.state[type].concat(id)
            })    
            break;
        case 'remove':
            this.setState({
                [type]: this.state[type].filter(item => item.id !== id)
            })
            break;
    }
}