正则表达式实现render函数

Question

请问下为什么没替换成功？打印信息为：name/${name}/'xiaoming'theageof${name}is${age}age/${age}/8theageof${name}is${age}consttemplate="theageof${name}is${age}";constdata={name:"xiaoming",age:8};console.log(render(template,data));//输出:"theageofxiaomingis8"functionrender(template,data){for(keyindata){if(key){console.log(key);varre=newRegExp("\$\{"+key+"\}");console.log(re,data[key]);varans=template.replace(re,data[key]);//console.log("test:",template.replace("${name}","xiaoming"));console.log(ans);}}}

Answer 1

$表示字符串的结尾，是特殊字符，使用RegExp的时候，需要使用两个\\转义：
consttemplate="theageof${name}is${age}";
constdata={name:"xiaoming",age:8};
console.log(render(template,data));
//输出:"theageofxiaomingis8"
functionrender(template,data){
for(keyindata){
if(key){
console.log(key);
varre=newRegExp("\\${"+key+"}");
//varre="${"+key+"}";//这块直接使用字符串就行，不用正则也可以
console.log(re,data[key]);
template=template.replace(re,data[key]);
//console.log("test:",template.replace("${name}","xiaoming"));
console.log(template);
}
}
}
                            

Answer 2

consttemplate="theageof${name}is${age}";
constdata={name:"xiaoming",age:8};
console.log(render(template,data));
functionrender(template,data){
varreg=/\$\{(\w*)\}/g;
returntemplate.replace(reg,function(a,b){
varval=data[b];
//可以抛出错误也可以给个默认空字符串
if(val===undefined)thrownewTypeError('Cannotreadproperty"'+b+'"ofundefined');
returnval;
})
}