鍦↗avaScript涓紝鍙互閫氳繃浠ヤ笅涓ょ鏂瑰紡瀹氫箟鏁扮粍闀垮害锛?/p>

1. 浣跨敤鏁扮粍鐨刲ength灞炴€э細鍙互閫氳繃涓簂ength灞炴€ц祴鍊兼潵鏀瑰彉鏁扮粍鐨勯暱搴︺€傚鏋滃皢length灞炴€ц缃负涓€涓皬浜庡綋鍓嶆暟缁勯暱搴︾殑鍊硷紝鏁扮粍浼氳鎴柇涓烘寚瀹氶暱搴︼紱濡傛灉灏唋ength灞炴€ц缃负涓€涓ぇ浜庡綋鍓嶆暟缁勯暱搴︾殑鍊硷紝鏁扮粍浼氳鎵╁睍锛屾柊鐨勪綅缃細鐢╱ndefined濉厖銆?/li>

绀轰緥锛?/p>

var arr = [1, 2, 3, 4, 5];
console.log(arr.length); // 杈撳嚭 5
arr.length = 3;
console.log(arr); // 杈撳嚭 [1, 2, 3]
arr.length = 7;
console.log(arr); // 杈撳嚭 [1, 2, 3, undefined, undefined, undefined, undefined]

2. 浣跨敤鏁扮粍瀛楅潰閲忕殑鏂瑰紡鍒濆鍖栨暟缁勬椂锛屽彲浠ュ湪鏂规嫭鍙蜂腑鐩存帴鎸囧畾鏁扮粍鐨勯暱搴︼紝鐒跺悗鐢ㄩ€楀彿鍒嗛殧姣忎釜鍏冪礌鐨勫€笺€傚鏋滄寚瀹氱殑闀垮害澶т簬鍒濆鍖栫殑鍏冪礌涓暟锛屽墿浣欑殑浣嶇疆浼氱敤undefined濉厖銆?/li>

绀轰緥锛?/p>

var arr = new Array(5); // 瀹氫箟涓€涓暱搴︿负5鐨勬暟缁?/span>
console.log(arr); // 杈撳嚭 [undefined, undefined, undefined, undefined, undefined]
var arr2 = [1, 2, 3, 4, 5]; // 瀹氫箟涓€涓湁5涓厓绱犵殑鏁扮粍
console.log(arr2); // 杈撳嚭 [1, 2, 3, 4, 5]

鎬荤粨锛氬湪JavaScript涓紝鏁扮粍闀垮害鏄姩鎬佸彲鍙樼殑锛屽彲浠ヤ娇鐢╨ength灞炴€ф潵鏀瑰彉鏁扮粍鐨勯暱搴︼紝涔熷彲浠ュ湪鍒濆鍖栨暟缁勬椂鎸囧畾闀垮害銆?/p>