javascript - 如何提高 UglifyJsPlugin 的性能

Question

在没有 UglifyJsPlugin 的情况下重建一个复杂的模块大约需要 25 秒，而在没有 UglifyJsPlugin 的情况下则需要 1 分钟多一点。平均而言，完整的构建花费 60-90% 的执行时间在 UglifyJsPlugin 中，我想知道我是否做错了什么，或者这就是事实。

使用:节点8.1.4npm 5.2.0网页包 3.2.0uglifyjs-webpack-插件 0.4.6uglify-js:2.8.29

选项:

const UGLIFYJS_OPTIONS = {
    compress: {
        sequences: true,        // join consecutive simple statements using the comma operator
        properties: true,       // rewrite property access using the dot notation, for example foo["bar"] ? foo.bar
        dead_code: true,        // remove unreachable code
        drop_debugger: true,    // remove debugger; statements
        unsafe: false,          // apply "unsafe" transformations
        conditionals: true,     // apply optimizations for if-s and conditional expressions
        comparisons: true,      // apply certain optimizations to binary nodes
        evaluate: true,         // attempt to evaluate constant expressions
        booleans: true,         // various optimizations for boolean context
        loops: true,            // optimizations for do, while and for loops when we can statically determine the condition
        unused: true,           // drop unreferenced functions and variables
        hoist_funs: true,       // hoist function declarations
        hoist_vars: false,      // hoist var declarations (this is false by default because it seems to increase the size of the output in general)
        if_return: true,        // optimizations for if/return and if/continue
        join_vars: true,        // join consecutive var statements
        cascade: true,          // small optimization for sequences, transform x, x into x and x = something(), x into x = something()
        collapse_vars: false,   // Collapse single-use var and const definitions when possible.
        warnings: false,        // display warnings when dropping unreachable code or unused declarations etc.
        negate_iife: true,      // negate "Immediately-Called Function Expressions" where the return value is discarded, to avoid the parens that the code generator would insert.
        pure_getters: false,    // If you pass true for this, UglifyJS will assume that object property access (e.g. foo.bar or foo["bar"]) doesn't have any side effects.
        pure_funcs: null,       // You can pass an array of names and UglifyJS will assume that those functions do not produce side effects.
        drop_console: false,    // Pass true to discard calls to console.* functions.
        keep_fargs: true,       // Prevents the compressor from discarding unused function arguments. You need this for code which relies on Function.length.
        keep_fnames: false      // Pass true to prevent the compressor from mangling/discarding function names. Useful for code relying on Function.prototype.name.
    },
    sourceMap: true,
    output: {
        comments: function (node/*: any*/, comment/*: any*/) {
            if (comment.type === 'comment2') {
                // multiline comment
                return /@preserve/i.test(comment.value);
            }

            return false;
        }
    }
};

Answer 1

禁用compress并仅启用mangle以非常快速地缩小文件大小并保持可接受的文件大小。

参见:https://github.com/mishoo/UglifyJS2#uglify-fast-minify-mode