javascrpt if

一个函数里面多了一个if，就运行报错。把那个if单独拿出来用一个函数来封装，代码是一样的。就正常运行。为什么？头大。

if又不是else，为什么要和之前那个的花括号写在一排

这么多if，到底哪个if报错？

可以把第二个 if 改为 else if

songplay(state,value){
    if(state.songdex===null){
        console.log('数据为空'）
    }
    else if(value=='low'){
        if(state.songdex < state.datasong.length-1) {
            state.songdex =state.songdex+1
            console.log(“当前音频索引值",state.index)
            state.audio.src=state.datasong[state.songdex].songsrc /∥载入当前上一首音频地址
            state.picturesrc = state.datasong[state.songdex].picturesrc
            state.audio.load()
        }
    }
    else if(value=='per'){
        if(state.songdex > 0){
            state.songdex =state.songdex-1
            console.log("当前音频索引值",state.index)
            state.audio.src =state.datasong[state.songdex].songsrc //载入当前上一首音频
            state.picturesrc = state.datasong[state.songdex].picturesrc
            state.audio.load()
            state.audio.play()
        }
    }
    else{
        state.songdex = value //存放当前在本数据组下音频索引值
        state.audio.src=state.datasong[state.songdex].songsrc //载入当前音频地址
        state.picturesrc =state.datasong[state.songdex].picturesrc //当前音频图片地址
        state.audio.load()
        state.audio.play()//当前播放状态
        state.paused = state.audio.paused
        state.ended = state.audio.ended
        console.log("paused"+state.paused)
        console.log("当前音频索引值",state.datasong[state.songdex+1].songsrc)
    }
}