模拟微任务 判断是否有对应的api

if(typeof Promise !=='undefined'&&isNative(Promise)){

}

function runMicrotask(func){
    if(typeof Promise==='function'){
        Promise.resolve().then(func)
        return
    }
    if(typeof MutationObserver==='function'){
        var ob=new MutationObserver(func)
        var node=document.createTextNode('')
        ob.observe(node,{characterData:true})
        node.data=1;
    }
    if(process&&typeof process.nextTick==='function'){
        process.nextTick(func)
        return
    }
    if(typeof setImmediate==='function'){
        setImmediate(func)
        return
    }
    setTimeout(func)
}