this.arr = []; // 存储所有历史价格，通过索引快速获取对应价格
传统建筑劳务市场，最大的痛点是信息不对称。工人们常常是“考勤时只张嘴、结款时跑断腿”。这种依靠人际关系的用工管理，给项目方和劳动者都带来极大的不确定性。
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Volatility and unusual structure at Stamford Bridge leave club’s young manager with a big test to rebuild like his rival has at Arsenal
when adding it to that array, then you can have unref clean up recursively: