// The WeakMap constructor can take an argument that is an array of pairs. var k1 = {}; var v1 = 42; var k2 = {}; var v2 = 43; var k3 = {}; var arr = [[k1, v1], [k2, v2]]; var m = new WeakMap(arr); assertEq(m.has(k1), true); assertEq(m.has(k2), true); assertEq(m.has(k3), false); assertEq(m.get(k1), v1); assertEq(m.get(k2), v2); assertEq(m.get(k3), undefined); var arraylike1 = { 0: k1, 1: v1 }; var arraylike2 = { 0: k2, 1: v2 }; arr = [arraylike1, arraylike2]; m = new WeakMap(arr); assertEq(m.has(k1), true); assertEq(m.has(k2), true); assertEq(m.has(k3), false); assertEq(m.get(k1), v1); assertEq(m.get(k2), v2); assertEq(m.get(k3), undefined);