用js做这个： 计算1-100之间所有数字的和 求答案,谢谢

<span class="hljs-built_in">var</span> <span class="hljs-built_in">num</span>=<span class="hljs-number">100</span>;
        <span class="hljs-built_in">var</span> <span class="hljs-built_in">sum</span>=<span class="hljs-number">0</span>;
        <span class="hljs-keyword">for</span>(<span class="hljs-built_in">var</span> i=<span class="hljs-number">0</span>;i<=<span class="hljs-built_in">num</span>;i++){
            <span class="hljs-built_in">sum</span> += i;
        }
        console.<span class="hljs-built_in">log</span>(<span class="hljs-string">"1-100所有数和为："</span>+ <span class="hljs-built_in">sum</span>);

<span class="hljs-regexp">//</span> 利用等差数列求和公式
const n = <span class="hljs-number">100</span>,  <span class="hljs-regexp">//</span>项数
     a1 = <span class="hljs-number">1</span>,  <span class="hljs-regexp">//</span>首项
     an = <span class="hljs-number">100</span>; <span class="hljs-regexp">//</span>末项
let Sn = (a1 + an) * n <span class="hljs-regexp">/ 2; /</span><span class="hljs-regexp">/和</span>

<span class="hljs-meta"><!DOCTYPE <span class="hljs-keyword">html</span>></span>
<span class="hljs-tag"><<span class="hljs-name">html</span>></span>
    <span class="hljs-tag"><<span class="hljs-name">head</span>></span>
        <span class="hljs-tag"><<span class="hljs-name">meta</span> <span class="hljs-attr">charset</span>=<span class="hljs-string">"utf-8"</span>></span>
        <span class="hljs-tag"><<span class="hljs-name">title</span>></span><span class="hljs-tag"></<span class="hljs-name">title</span>></span>
    <span class="hljs-tag"></<span class="hljs-name">head</span>></span>
    <span class="hljs-tag"><<span class="hljs-name">body</span>></span>
        <span class="hljs-tag"><<span class="hljs-name">script</span>></span><span class="language-javascript">
                    <span class="hljs-keyword">var</span> num=<span class="hljs-number">100</span>;
                    <span class="hljs-keyword">var</span> sum=<span class="hljs-number">0</span>;
                    <span class="hljs-keyword">for</span>(<span class="hljs-keyword">var</span> i=<span class="hljs-number">0</span>;i<=num;i++){
                        sum += i;
                    }
                    <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">write</span>(<span class="hljs-string">"1-100所有数和为："</span>+ sum);
        </span><span class="hljs-tag"></<span class="hljs-name">script</span>></span>
    <span class="hljs-tag"></<span class="hljs-name">body</span>></span>
<span class="hljs-tag"></<span class="hljs-name">html</span>></span>

加油哦