js计算本地缓存

主要的思想：获取所有子项长度，进行叠加得出缓存使用的大小

function getStorageSize(storage){
    if(typeof storage !== 'object' || storage === null){
         throw new Error('计算的缓存不合法');   
    }else{
        var size = 0;
        for(item in storage) {
            if(storage.hasOwnProperty(item)) {
                size += storage.getItem(item).length;
            }
        }
        return Number((size / 1024).toFixed(2));
    }
}
var localSize = getStorageSize(window.localStorage);
console.log('localStorage当前大小', localSize, 'kb');
var sessionSize =getStorageSize(window.sessionStorage);
console.log('sessionStorage当前大小', sessionSize, 'kb');