react reselect性能优化避免数据重复计算

[chenchenyuyu]

避免不必要的重复计算

let memoizeState = null
function mapStateToProps(state) {
    const {a, b, c} = state
    if (!memoizeState) { 
       memoizeState =  {
            a,
            b,
            c,
            fab: f(a,b),
            hbc: h(b,c),
            gac: g(a,c),
            uabc: u(a, b, c)
        }
    } else {
        if (!(a === memoizeState.a && b === memoizeState.b) ) {
            // f should invoke
            memoizeState.fab = f(a, b)
        }
        if (!(b === memoizeState.b && c === memoizeState.c) ) {
            // h should invoke
            memoizeState.hbc = h(b, c)
        }
        if (!(a === memoizeState.a && c === memoizeState.c) ) {
            // g should invoke
            memoizeState.gac = g(a, c)
        }
        if (!(a === memoizeState.a && b === memoizeState.b && c === memoizeState.c) ) {
            // u should invoke
            memoizeState.uabc = u(a, b, c)
        }
        memoizeState.a = a
        memoizeState.b = b
        memoizeState.c = c
    }

    return memoizeState
}

参考： https://juejin.im/post/5a04825b6fb9a0450f216459