CoffeeScript 字符串 - substr()
描述
此方法用于返回字符串的所需子字符串。 它接受一个整数值，指示子字符串的起始值和字符串的长度，并返回所需的子字符串。 如果起始值为负数，则 substr() 方法将其用作从字符串末尾开始的字符索引。
语法
下面给出的是 JavaScript 的 substr() 方法的语法。 我们可以在 CoffeeScript 代码中使用相同的方法。
string.substr(start[, length])
示例
以下示例演示了在 CoffeeScript 代码中使用 JavaScript 的 substr() 方法。 将此代码保存在名为 string_substr.coffee 的文件中
str = "Apples are round, and apples are juicy.";
console.log "The sub string having start and length as (1,2) is : " + str.substr 1,2
console.log "The sub string having start and length as (-2,2) is : " + str.substr -2,2
console.log "The sub string having start and length as (1) is : " + str.substr 1
console.log "The sub string having start and length as (-20, 2) is : " + str.substr -20,2
console.log "The sub string having start and length as (20, 2) is : " + str.substr 20,2;
打开命令提示符并编译.coffee 文件，如下所示。
c:\> coffee -c coffee string_substr.coffee
在编译时，它会提供以下 JavaScript。
// Generated by CoffeeScript 1.10.0
(function() {
var str;
str = "Apples are round, and apples are juicy.";
console.log("The sub string having start and length as (1,2) is : " + str.substr(1, 2));
console.log("The sub string having start and length as (-2,2) is : " + str.substr(-2, 2));
console.log("The sub string having start and length as (1) is : " + str.substr(1));
console.log("The sub string having start and length as (-20, 2) is : " + str.substr(-20, 2));
console.log("The sub string having start and length as (20, 2) is : " + str.substr(20, 2));
}).call(this);
现在，再次打开命令提示符 并运行 CoffeeScript 文件，如下所示。
c:\> coffee string_substr.coffee
执行时，CoffeeScript 文件产生以下输出。
The sub string having start and length as (1,2) is : pp The sub string having start and length as (-2,2) is : y. The sub string having start and length as (1) is : pples are round, and apples are juicy. The sub string having start and length as (-20, 2) is : nd The sub string having start and length as (20, 2) is : d
