使用parseFloat即可:

<span style="color:#dcc6e0">const</span> str = <span style="color:#abe338">&quot;3.14&quot;</span>;
<span style="color:#dcc6e0">const</span> floatValue = <span style="color:#f5ab35">parseFloat</span>(str);
<span style="color:#f5ab35">console</span>.log(floatValue); <span style="color:#d4d0ab">// 输出 3.14</span>