javascript如何获取字符串长度

<script>

    var str = '飞鸟慕鱼博客';

    var len = str.replace(/[^\x00-\xff]/g, "00").length;

    console.log(len);

</script>

<script>

    var str = '中华人民共和国';

    var len = 0;

    for (var i = 0; i < str.length; i++) {

        var c = str.charAt(i);

        if (escape(c).length > 4) {

            len += 2;

        } else if (c != "\r") {

            len++;

        }

    }  

    console.log(len);

</script>

<script>

    var str = '这里使用的正规表达式';

    var len = 0;

    for (var i = 0; i < str.length; i++) {

        var a = str.charAt(i);

        //使用的正则表达式

        if (a.match(/[^\x00-\xff]/ig) != null) {

            len += 2;

        } else {

            len += 1;

        }

    }  

    console.log(len);

</script>

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