Underscore.js是否具备类似C++ sprintf()的字符串拼接与变量替换功能？

Hey there! Let's tackle your two questions step by step.

1. 手动实现字符串拼接并将变量替换为下划线 #

Depending on your exact use case, here are a couple of practical approaches:

Scenario 1: Template-based variable replacement (with underscores matching value length) #

If you're working with a template string that has placeholders for variables, you can write a simple function to replace each placeholder with underscores of the same length as the original variable value:

function swapVarsWithUnderscores(templateStr, variables) {
  // Match placeholders like {varName}
  return templateStr.replace(/\{(\w+)\}/g, (match, varKey) => {
    // Get the original variable value (default to empty string if missing)
    const varValue = variables[varKey] || '';
    // Return underscores equal to the value's length
    return '_'.repeat(varValue.length);
  });
}

// Example usage
const userTemplate = 'Profile: {name} | {role} | {department}';
const userInfo = { name: 'Alice Smith', role: 'Senior Dev', department: 'Engineering' };
const processedStr = swapVarsWithUnderscores(userTemplate, userInfo);
console.log(processedStr);
// Output: "Profile: __________ | _________ | ___________"

Scenario 2: Basic string concatenation + replacement #

If you just need to concatenate multiple strings first, then replace specific variable markers with underscores:

// Step 1: Concatenate your base strings
const partA = 'Hello, my name is ';
const partB = ' and I work at ';
const fullTemplate = partA + '{name}' + partB + '{company}';

// Step 2: Replace variables with underscores
const finalStr = fullTemplate.replace(/\{name\}/g, '______').replace(/\{company\}/g, '________');
console.log(finalStr);
// Output: "Hello, my name is ______ and I work at ________"

2. Does Underscore.js offer sprintf-like string concatenation and variable replacement? #

Great question! Underscore.js doesn't have a direct equivalent to C++'s sprintf() function out of the box, but it does have powerful template utilities that can handle variable replacement (including swapping variables for underscores).

Using _.template() for variable replacement #

Underscore's _.template() is designed to render dynamic templates by replacing placeholders with values. To use it for your underscore replacement needs, you just need to pass in an object where each value is a string of underscores (matching the length of your original variables, if needed):

// Define your Underscore template (uses <%= %> as default placeholders)
const underscoreTemplate = _.template('User: <%= username %> | Status: <%= accountStatus %>');

// Original variable data
const userData = { username: 'bob123', accountStatus: 'Active' };

// Convert values to underscores of matching length
const underscoreValues = _.mapObject(userData, val => '_'.repeat(val.length));

// Render the template
const result = underscoreTemplate(underscoreValues);
console.log(result);
// Output: "User: ______ | Status: ______"

If you need more formatted string handling (like sprintf's type specifiers), you'd have to either wrap Underscore's tools in a custom function or pair it with a dedicated sprintf library—but for basic variable replacement and underscore swapping, _.template() works perfectly.

内容的提问来源于stack exchange，提问作者sazr