I和f不是变量。将变量存储到字符串中

name = "John"
age = 25
message = "My name is %s and I am %d years old." % (name, age)
# 或者使用format()函数
message = "My name is {} and I am {} years old.".format(name, age)

var name = "John";
var age = 25;
var message = "My name is " + name + " and I am " + age + " years old.";

var ejs = require('ejs');
var name = "John";
var age = 25;
var template = "My name is <%= name %> and I am <%= age %> years old.";
var message = ejs.render(template, {name: name, age: age});