How to use JavaScript to realize a two-level linkage drop-down box

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Javascript is a case-sensitive client scripting language for object-oriented dynamic types, which is developed from Netscape's LiveScript. The main purpose is to solve the speed problem left over by server-side languages, such as Perl, and to provide customers with smoother browsing results.

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New Document / / defines a two-dimensional array of cities in the same order as the provinces. Obtain the corresponding city array var city= ["Beijing", "Tianjin", "Shanghai", "Chongqing"], ["Nanjing", "Suzhou", "Nantong", "Changzhou"], ["Fuzhou", "Fu'an", "Longyan", "Nanping"], [Guangzhou "," Chaoyang "," Chaozhou "," Chenghai "], [Lanzhou"]. "Baiyin", "Dingxi", "Dunhuang"] Function getCity () {/ / get the object of the province drop-down box var sltProvince=document.form1.province; / / get the city drop-down box object var sltCity=document.form1.city; / / get the city array var provinceCity=city of the corresponding province [sltProvince.selectedIndex-1]; / / clear the city drop-down box, leaving only the prompt option sltCity.length=1; / / populate the city drop-down box with the values in the city drop-down box for (var icities 0 countries I