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var unparse = require('escodegen').generate;
module.exports = function (ast, vars) {
if (!vars) vars = {};
var FAIL = {};
var result = (function walk (node, scopeVars) {
if (node.type === 'Literal') {
return node.value;
}
else if (node.type === 'UnaryExpression'){
var val = walk(node.argument)
if (node.operator === '+') return +val
if (node.operator === '-') return -val
if (node.operator === '~') return ~val
if (node.operator === '!') return !val
return FAIL
}
else if (node.type === 'ArrayExpression') {
var xs = [];
for (var i = 0, l = node.elements.length; i < l; i++) {
var x = walk(node.elements[i]);
if (x === FAIL) return FAIL;
xs.push(x);
}
return xs;
}
else if (node.type === 'ObjectExpression') {
var obj = {};
for (var i = 0; i < node.properties.length; i++) {
var prop = node.properties[i];
var value = prop.value === null
? prop.value
: walk(prop.value)
;
if (value === FAIL) return FAIL;
obj[prop.key.value || prop.key.name] = value;
}
return obj;
}
else if (node.type === 'BinaryExpression' ||
node.type === 'LogicalExpression') {
var l = walk(node.left);
if (l === FAIL) return FAIL;
var r = walk(node.right);
if (r === FAIL) return FAIL;
var op = node.operator;
if (op === '==') return l == r;
if (op === '===') return l === r;
if (op === '!=') return l != r;
if (op === '!==') return l !== r;
if (op === '+') return l + r;
if (op === '-') return l - r;
if (op === '*') return l * r;
if (op === '/') return l / r;
if (op === '%') return l % r;
if (op === '<') return l < r;
if (op === '<=') return l <= r;
if (op === '>') return l > r;
if (op === '>=') return l >= r;
if (op === '|') return l | r;
if (op === '&') return l & r;
if (op === '^') return l ^ r;
if (op === '&&') return l && r;
if (op === '||') return l || r;
return FAIL;
}
else if (node.type === 'Identifier') {
if ({}.hasOwnProperty.call(vars, node.name)) {
return vars[node.name];
}
else return FAIL;
}
else if (node.type === 'ThisExpression') {
if ({}.hasOwnProperty.call(vars, 'this')) {
return vars['this'];
}
else return FAIL;
}
else if (node.type === 'CallExpression') {
var callee = walk(node.callee);
if (callee === FAIL) return FAIL;
if (typeof callee !== 'function') return FAIL;
var ctx = node.callee.object ? walk(node.callee.object) : FAIL;
if (ctx === FAIL) ctx = null;
var args = [];
for (var i = 0, l = node.arguments.length; i < l; i++) {
var x = walk(node.arguments[i]);
if (x === FAIL) return FAIL;
args.push(x);
}
return callee.apply(ctx, args);
}
else if (node.type === 'MemberExpression') {
var obj = walk(node.object);
// do not allow access to methods on Function
if((obj === FAIL) || (typeof obj == 'function')){
return FAIL;
}
if (node.property.type === 'Identifier') {
return obj[node.property.name];
}
var prop = walk(node.property);
if (prop === FAIL) return FAIL;
return obj[prop];
}
else if (node.type === 'ConditionalExpression') {
var val = walk(node.test)
if (val === FAIL) return FAIL;
return val ? walk(node.consequent) : walk(node.alternate)
}
else if (node.type === 'ExpressionStatement') {
var val = walk(node.expression)
if (val === FAIL) return FAIL;
return val;
}
else if (node.type === 'ReturnStatement') {
return walk(node.argument)
}
else if (node.type === 'FunctionExpression') {
var bodies = node.body.body;
// Create a "scope" for our arguments
var oldVars = {};
Object.keys(vars).forEach(function(element){
oldVars[element] = vars[element];
})
node.params.forEach(function(key) {
if(key.type == 'Identifier'){
vars[key.name] = null;
}
});
for(var i in bodies){
if(walk(bodies[i]) === FAIL){
return FAIL;
}
}
// restore the vars and scope after we walk
vars = oldVars;
var keys = Object.keys(vars);
var vals = keys.map(function(key) {
return vars[key];
});
return Function(keys.join(', '), 'return ' + unparse(node)).apply(null, vals);
}
else if (node.type === 'TemplateLiteral') {
var str = '';
for (var i = 0; i < node.expressions.length; i++) {
str += walk(node.quasis[i]);
str += walk(node.expressions[i]);
}
str += walk(node.quasis[i]);
return str;
}
else if (node.type === 'TaggedTemplateExpression') {
var tag = walk(node.tag);
var quasi = node.quasi;
var strings = quasi.quasis.map(walk);
var values = quasi.expressions.map(walk);
return tag.apply(null, [strings].concat(values));
}
else if (node.type === 'TemplateElement') {
return node.value.cooked;
}
else return FAIL;
})(ast);
return result === FAIL ? undefined : result;
};
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